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Dynamics of circulating concentrations of gonadotropins and ovarian hormones throughout the menstrual cycle in the bonnet monkey role of inhibin A in the regulation of follicle-stimulating hormone secretion.

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American Journal of Primatology 71:817–824 (2009)
RESEARCH ARTICLE
Dynamics of Circulating Concentrations of Gonadotropins and Ovarian
Hormones Throughout the Menstrual Cycle in the Bonnet Monkey: Role
of Inhibin A in the Regulation of Follicle-Stimulating Hormone Secretion
P.S. SURESH1 AND R. MEDHAMURTHY1,2
1
Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India
2
Primate Research Laboratory, Indian Institute of Science, Bangalore, India
In higher primates, increased circulating follicle-stimulating hormone (FSH) levels seen during late
menstrual cycle and during menstruation has been suggested to be necessary for initiation of follicular
growth, recruitment of follicles and eventually culminating in ovulation of a single follicle. With a view
to establish the dynamics of circulating FSH secretion with that of inhibin A (INH A) and progesterone
(P4) secretions during the menstrual cycle, blood was collected daily from bonnet monkeys beginning
day 1 of the menstrual cycle up to 35 days. Serum INH A levels were low during early follicular phase,
increased significantly coinciding with the mid cycle luteinizing hormone (LH) surge to reach maximal
levels during the mid luteal phase before declining at the late luteal phase, essentially paralleling the
pattern of P4 secretion seen throughout the luteal phase. Circulating FSH levels were low during early
and mid luteal phases, but progressively increased during the late luteal phase and remained high for
few days after the onset of menses. In another experiment, lutectomy performed during the mid luteal
phase resulted in significant decrease in INH A concentration within 2 hr (58.372 vs. 27.373 pg/mL),
and a 2- to 3-fold rise in circulating FSH levels by 24 hr (0.2070.02 vs. 0.5370.14 ng/mL) that remained
high until 48 hr postlutectomy. Systemic administration of Cetrorelix (150 mg/kg body weight), a
gonadotropin releasing hormone receptor antagonist, at mid luteal phase in monkeys led to suppression
of serum INH A and P4 concentrations 24 hr post treatment, but circulating FSH levels did not change.
Administration of exogenous LH, but not FSH, significantly increased INH A concentration. The
results taken together suggest a tight coupling between LH and INH A secretion and that INH A is
largely responsible for maintenance of low FSH concentration seen during the luteal phase. Am. J.
Primatol. 71:817–824, 2009.
r 2009 Wiley-Liss, Inc.
Key words: Bonnet monkey; corpus luteum; LH; FSH; INH A; P4; GnRH-R antagonist
INTRODUCTION
The main functions of the ovary, viz, steroidogenesis and gametogenesis, are regulated principally by
pituitary gonadotropins, follicle-stimulating hormone
(FSH) and luteinizing hormone (LH). However, the
female gonad in addition to secretion of steroids is also
a site of synthesis and secretion of proteinaceous
hormones such as inhibin, relaxin, oxytocin etc. Inhibin
(INH) is a heterodimeric glycoprotein that comprises of
a-subunit and one of the two different b subunits [bA
and bB subunits to form inhibin A (INH A) (a and bA)
and INH B (a and bB) isoforms], produced primarily by
granulosa and granulosa-lutein cells (luteal cells) in the
ovary [De Jong, 1988; Mather et al., 1992, 1997; Ying,
1988]. By definition, both INH isoforms suppress basal
as well as gonadotropin releasing hormone (GnRH)stimulated secretion of pituitary FSH with effects on
LH secretion has been suggested to be minimal
r 2009 Wiley-Liss, Inc.
[Burger, 1993; Plant et al., 1991]. Several studies have
established that INHs have potentially complex interdependent endocrine, autocrine and paracrine functions essential for the regulation of growth and
development of the ovulating follicle [de Kretser
et al., 2002; Laven & Fauser, 2004]. During the
macaque menstrual cycle, it was observed that
immunoreactive INH levels were highest at the mid
luteal phase and the levels could be suppressed by
Correspondence to: Dr. R. Medhamurthy, Department
of Molecular Reproduction, Development and Genetics,
Indian Institute of Science, Bangalore-560012, India.
E-mail: rmm@mrdg.iisc.ernet.in
Received 11 December 2008; revised 15 April 2009; revision
accepted 20 April 2009
DOI 10.1002/ajp.20709
Published online 18 May 2009 in Wiley InterScience (www.
interscience.wiley.com).
818 / Suresh and Medhamurthy
treatment with GnRH receptor antagonist, suggesting
that INH is synthesized in the CL and that its secretion
is integrated to the gonadotropin control of luteal
function [Fraser et al., 1989]. Furthermore, the
lutectomy experiment performed during mid luteal
phase in monkeys clearly established the link between
the presence of CL and circulating immunoreactive
INH [Bassetti et al., 1990]. However, following development of specific assays for INH A and INH B, it was
established that INH A secretion is highest during the
luteal phase, while the high INH B circulating
concentrations are observed only during the follicular
phase, which originated from antral follicles and the
dominant follicle destined for ovulation in women
[Groome et al., 1996; Welt et al., 1999]. In higher
primates, it is well established that circulating LH is
essential for the maintenance of structure and function
of CL [Zeleznik & Benyo, 1994]; however, whether LH
controls INH A secretion during the luteal phase
remains to be determined. Although FSH is regarded
as the principal stimulus for INH secretion [Brannian
et al., 1992], its role in the regulation of INH A
secretion during the luteal phase is not known. In
monkeys and women, administration of GnRH receptor
antagonist has been shown to disrupt pituitary
gonadotropin secretion and termination of the luteal
phase [Duffy et al., 1999; Fraser et al., 1999; Yadav &
Medhamurthy, 2006]. Previous work in the laboratory
has confirmed that molecular markers of luteolysis
including down regulation of expression of genes
associated with steroidogenesis were demonstrable in
CL collected 24–48 hr post GnRH receptor antagonist
treatment [Yadav & Medhamurthy, 2006]. Recently,
employing the GnRH receptor antagonist-induced
model, we have demonstrated rescue of CL function
with respect to progesterone (P4) secretion by exogenous LH replacement [Priyanka et al., 2009]. In light of
the above information, the present experiments were
carried out with the following objectives: (i) to establish
various endocrine hormone profiles throughout the
menstrual cycle in the bonnet monkey with emphasis
on characterization of circulating concentrations of
INH A and FSH prior to ovulation and during the
period of late menstrual period, (ii) to study the
effects of lutectomy on dynamics of ovarian hormones
and FSH secretion and, (iii) to examine the effects
of replacement of exogenous LH or FSH on INH
A secretion during the GnRH antagonist-induced
luteolysis.
METHODS
Animals
Experiments involving monkeys in the study
were cleared by the Institutional Animal Ethics
Committee of the Indian Institute of Science,
Bangalore. The experimental procedures followed
are based on guidelines formulated by Indian
National Science Academy and Indian Institute of
Am. J. Primatol.
Science, India. Adult female bonnet monkeys
(Macaca radiata) weighing 3.8–4.5 kg and with a
history of regular menstrual cyclicity (27–29 days
length) were housed in individual stainless steel
cages (eight monkeys of both sexes per room). The
animals were maintained under a controlled photoperiod (12L:12D, lights on 0600 hr and lights off
1800 hr). During the study period performed during
August to January months of the year the temperature in the animal rooms with provision for continuous change of fresh air, ranged from 22–281C
(dry-bulb temperature) to 17–221C (wet-bulb temperature) maximum and minimum, respectively.
Monkeys in the colony were fed a single daily
meal between 1100 and 1200 hr that consisted of
pellet food and supplemented with carrot, banana
and sweet lime as been described previously
[Medhamurthy et al., 2007]. Monkeys were also
provided nutritional supplements such as Iron syrup
preparation and high protein biscuits at monthly
intervals.
Experiment 1: Hormone Concentrations
During the Normal Menstrual Cycle
Four adult female bonnet monkeys were monitored daily for the onset of menses. Blood samples
(1.5 mL) through femoral venipuncture were collected
between 0900 and 1000 hr daily beginning day 1 of the
menses for up to 35 days. Blood samples were stored
overnight at 41C and the serum was separated by
centrifugation and stored at 201C until assayed.
Experiment 2: Effects of Lutectomy on
Dynamics of Ovarian Hormone and FSH
Secretions
Adult female bonnet monkeys were observed
daily for the onset of menses and blood samples were
collected daily from day 8 to 12 of the menstrual
cycle for determining the onset of estradiol (E2) and
LH surges. The day of peak LH surge was designated
as day 0, and one day after day 0 of peak LH surge
was designated as day 1 of the luteal phase.
Additional blood samples were collected on day 3
and 5 of the luteal phase to confirm for the rise in
circulating P4 for the presence of functional CL.
Lutectomy (n 5 4) was performed on day 8 of the
luteal phase by accessing the ovaries through mid
ventral laparotomy performed on ketamine hydrochloride (15 mg/kg body weight (BW) and pentobarbital sodium (8–12 mg/kg BW) anesthetized monkeys
under aseptic conditions. Blood samples were collected at different time intervals before and after
lutectomy for monitoring circulating hormones. In
another group of monkeys (n 5 4) not subjected to
surgical procedures, blood samples were collected at
similar intervals to that of lutectomy group.
Dynamics of Inhibin A and FSH Secretion / 819
Experiment 3: Concentrations of Circulating
Ovarian Hormones and FSH After Treatment
with GnRH Receptor Antagonist: Effects of LH
and FSH Replacements on INH A Secretion
Employing the induced luteolysis model system
reported recently from the laboratory [Priyanka
et al., 2009], circulating concentrations of E2, FSH
and INH A were determined. Also, effects of
replacement with LH or FSH during induced
luteolysis on secretion of INH A were examined.
For this purpose, monkeys were treated with
5.25% glucose solution (VEH, n 5 4) or CET (n 5 4)
150 mg/kg BW s.c., on day 7 of the luteal phase, and
blood samples were collected immediately before and
at different time intervals after VEH/CET treatment
for five days. Another group of monkeys (n 5 6) were
treated with CET on day 7 of the luteal phase for
24 hr, three of the monkeys were treated with a
single injection of recombinant human (rh) LH
(20 IU/kg BW i.v.). The dose was previously shown
to stimulate the secretion of circulating P4 in the
CET-treated monkeys suggestive of rescue of CL
function [Priyanka et al., 2009]. Another three
CET-treated monkeys received Gonal-Fs (recombinant hFSH preparation; 50 IU s.c.) as exogenous
FSH supplementation sufficient for the stimulation
of follicular growth in monkeys. Blood samples
were collected at 8 hr postexogenous gonadotropin
treatments.
Hormone Assays
Steroids (E2 and P4) in serum were determined
by specific RIA as reported previously [Selvaraj
et al., 1996]. The E2 (GDN ]244) and P4 (GDN
]337) antisera were kindly provided by Professor
G. D. Niswender, Colorado State University, Fort
Collins, CO. The sensitivities of the assays for E2 and
P4 were 39 pg/mL and 0.1 ng/mL, respectively. Interand intra-assay coefficients of variation for both the
hormones were o10%.
Gonadotropins
All samples from a series for a given animal were
analyzed in one assay. Serum LH was quantified
using a RIA kit supplied by the National Hormone
and Pituitary Program, USA. It consists of antirecombinant cynomolgus LH (AFP342994) raised in
rabbit and recombinant cynomolgus LH preparation,
NICHD-Rec-Mo-LH-RP-1 (AFP 6936A), which was
used both for iodination and preparation of standards. The antibody was used at a final assay tube
dilution of 1:750,000 in a total assay set-up volume of
300 mL. For construction of the standard curve, the
hormone standards employed ranged from 0.2 ng/mL
(minimum) to 10 ng/mL (maximum). To rule out the
possible serum effects (i.e. binding of tracer
to antibody is influenced by the presence of
nonspecific serum components), the reference
standards were prepared initially in the monkey
gonadotropin-free serum, but later replaced with
female ovine serum (heterologous sera as a substitute for monkey gonadotropin free-serum). The
average sensitivity of the assay was 0.2 ng NICHDRec-Mo-LH-RP-1/mL and the inter- and intra-assay
coefficients of variation were o10%.
Serum FSH was estimated using a monkey RIA
kit supplied by the National Hormone Pituitary
Program, USA. It consists of antirecombinant cynomolgus FSH (AFP782594) raised in rabbit and
rec-moFSH–RP-1 (AFP-6940 A), which was used
both for the preparation of standards and iodination.
The antibody was used at a final tube assay dilution
of 1:750,000 in a total set-up volume of 300 mL. The
standard curve was generated employing hormone
standards that ranged from 0.125 ng/mL (minimum)
to 8 ng/mL (maximum). It was observed that serum
influenced the binding by way of suppression of
binding. To rule out the serum effects, the hormone
standards were prepared in the bovine serum after
confirming that bovine gonadotropins did not cross
react with the antibody. The average sensitivity of
the assay was 0.125 ng NICHD-Rec-Mo-LH-RP-FSHRP-1/mL, and inter- and intra-assay coefficients of
variation were o10%.
Inhibin A
Concentrations of INH A in serum were measured using a commercially available Human ELISA
kit (cat] DSL-10-28100, Diagnostic System Laboratories, Webster, TX). The sensitivity of the assay was
1 pg/mL, and inter- and intra-assay coefficients of
variation were 7.6 and 6.2%, respectively.
Statistical Analysis
Wherever applicable, data were expressed as
mean7SEM. The data of multiple groups were
analyzed by one-way ANOVA, followed by the
Newman-Keuls multiple comparison test (PRISM
Graph pad, version 4; Graph Pad Software, Inc., San
Diego, CA). A P value of o0.05 was considered
statistically significant. Comparison between two
groups for each time point was done with Student’s
t-test.
RESULTS
Endocrine Hormone Concentrations
Throughout the Menstrual Cycle in Female
Monkeys
Circulating mean (7SEM) serum E2 and LH
concentrations throughout the menstrual cycle and
few days after the onset of second menses are
represented in Figure 1A. For calculation and
representation of hormone concentrations, the day
of peak LH surge was identified in each monkey and
Am. J. Primatol.
820 / Suresh and Medhamurthy
25
P4
INH A
2.0
1.0
1.5
0.75
250
150
10
5
50
-10 -8 -6 -4 -2 0
2
4
6
100
1.0
0.5
50
0.5
FSH (ng/ml)
15
P4(ng/ml)
200
E2, INH A (pg/ml)
20
100
0.25
8 10 12 14 16
3.5
100
3.0
80
-6
60
2.0
40
1.5
1.0
20
0.5
0
-5
-4
-3
-2
-1
0
1
2
Days before and after menses
2.5
FSH (ng/ml)
P4(ng/ml)
IINH A (pg/ml)
E2
FSH
150
300
LH (ng/ml)
E2(pg/ml)
350
Fig. 2. The hormone data 5 days prior to the onset of menses (see
Fig. 1) and hormone data from blood samples collected after the
onset of menses are plotted to indicate patterns of FSH and
ovarian hormone secretion during start of a new menstrual
cycle.
0.0
-10 -8 -6 -4 -2
0
2
4
6
8
10 12 14 16
Days before and after peak LH surge
Fig. 1. Top and bottom panels, circulating mean (7SEM)
concentrations of LH (solid square symbol), E2 (solid triangle),
FSH (inverted solid triangle), P4 (solid diamond) and INH A
(open circle) throughout the menstrual cycle of bonnet macaques. The day of peak LH surge concentration in each monkey
was identified and designated as day 0 (a vertical dotted line is
drawn between peak LH concentration and day 0) and circulating LH concentrations on different days before and after peak
LH surge were represented in relation to the peak concentration.
The days before peak LH surge were represented as decreasing
days (with negative notation).
was designated as day 0 of peak LH surge and all
data points before and after day 0 (of peak LH surge)
within each monkey was determined. The peak LH
surge occurred 12.370.33 days after the onset of
menses. The mean (7SEM) peak LH surge was
16.273.2 ng/mL (Fig. 1A), and the mean peak E2
concentration on the day of peak LH surge was
282.5733.5 pg/mL. Of the four monkeys, three had
their peak E2 levels on the day of LH peak surge,
but one monkey had high peak E2 surge level
(320 pg/mL) a day preceding the peak LH surge.
Mean (7SEM) hormone concentrations for each day
was calculated after aligning the day of peak LH
surge from all four monkeys. Circulating FSH
concentrations fluctuated during the follicular phase
(i.e. days preceding the onset of LH surge), but
increased coincident with the LH surge and peak
surge concentrations were 1.770.38 ng/mL (Fig. 1B).
After the surge period, mean FSH concentrations
remained low for most part of the luteal phase of
menstrual cycle, but increased few days immediately
before and after the onset of menses (Fig. 1B).
Circulating mean (7SEM) of P4 and INH A
concentrations throughout the menstrual cycle are
shown in Figure 1B. As can be seen from the figure,
serum P4 concentration was low on days preceding
the onset of LH surge, and progressively increased to
reach maximum concentrations 2.9370.20 ng/mL
7 days after peak LH surge, but the concentrations
began to decline thereafter and were lowest on the
Am. J. Primatol.
day of menses. Circulating INH A concentrations
were undetectable or low before the onset of
gonadotropin surge. Circulating INH A concentrations determined immediately prior to LH surge and
throughout the luteal phase revealed a pattern of
secretion similar to P4 with highest concentrations
seen 10–11 days postpeak LH surge, but thereafter
began to decline to reach lowest concentration on the
day of menses (Fig. 1B).
Dynamics of P4, INH A, E2 and FSH Secretion
During Late Menstrual Cycle and Menses
To establish interrelationship between FSH and
various ovarian hormones, circulating FSH concentrations along with P4, INH A and E2 concentrations
were assayed and plotted 5 days before and 2 days
after the onset of menses (Fig. 2). Circulating FSH
concentrations progressively increased before occurrence of menses, but declined 1 day prior to the onset
of menses. Circulating P4 concentrations 5 days prior
to the onset of menses was 1.6270.39 ng/mL and
declined to 0.3670.03 ng/mL on the day of menses.
Circulating concentrations of INH A 5 days prior to
the onset of menses were 81.9712.6 pg/mL, fell to
3.872.3 pg/mL on the day of menses and became
undetectable after the onset of menses (Fig. 2).
Circulating concentrations of E2 showed a progressive rise during the late luteal phase of the menstrual
cycle and after the onset of menses.
Effects of Lutectomy on Dynamics of FSH and
Ovarian Hormone Secretions
Circulating P4, INH A, E2 and FSH concentrations
immediately prior to and at different time points after
lutectomy are presented in Figure 3. Circulating
concentrations of P4 declined immediately after performing lutectomy on day 8 of the luteal phase and
the concentrations were significantly lower (Po0.05)
throughout the 96 hr period monitored compared with
concentrations in monkeys not subjected to lutectomy
Dynamics of Inhibin A and FSH Secretion / 821
5
3
*
*
2
*
b
1
b b
0.8
FSH (ng/ml)
*
*
0.6
b
40
20
a
*
b
*
a
72
L11
*
b
c
*
b
160
b
48
L10
60
c
a
0 12 24
L8
L9
80
bb
0.4
0.2
INH A (pg/ml)
**
a
E4(pg/ml)
P4(ng/ml)
4
100
96
L12
Time (h) post lutectomy
120
80
40
a a a
0 12 24
L8
L9
48
L10
72
L11
96
L12
Time (h) post lutectomy
Fig. 3. Circulating mean (7SEM) concentrations of FSH, INH A, P4 and E2 in monkeys subjected to lutectomy (solid line) on day 8 of the
luteal phase of the menstrual cycle. The concentrations of various hormones in monkeys not subjected to lutectomy (dotted line) are also
shown. Bars with different letters above them are significant (Po0.05) from each other. Po0.05 when analyzed with student’s t-test in
comparison to control and lutectomy animals, df 6 for each time points.
(Fig. 3). Circulating INH A concentrations, similar to
P4, also decreased (Po0.05) 2 hr after lutectomy and
remained low thereafter (Fig. 3). During the first 24 hr
after lutectomy, circulating E2 concentrations were not
significantly different from monkeys not subjected to
lutectomy, but the concentrations were significantly
(Po0.05) higher at 48 hr following lutectomy, and
remained high at 72 and 96 hr postlutectomy (Fig. 3).
Lutectomy on day 8 of the luteal phase of the
menstrual cycle resulted in rise in FSH concentration
24 hr postlutectomy and remained high (Po0.05) after
48 hr compared with concentrations in monkeys not
subjected to lutectomy (Fig. 3).
Patterns of FSH Secretion and Ovarian
Hormones Following Induction of Luteolysis
Administration of CET, a GnRH receptor antagonist, led to significant decrease in P4 concentration
within 12 hr after treatment (3.45 vs. 1.5 ng/mL at
0 and 12 hr, respectively; Fig. 4) and the levels
continued to decline throughout the observation
period (Fig. 4). Circulating concentrations of INH A
also decreased within 24 hr after CET treatment and
was 3.6471.07 pg/mL at 72 hr (Fig. 4). All monkeys
exhibited menses 96–120 hr post CET treatment.
Circulating E2 concentrations were lower (Po0.05)
after CET treatment, but tended to increase after
48 hr (Fig. 4). In contrast to the ovarian hormone
secretion patterns, concentrations of FSH although
tended to be lower at some time points, but did not
change significantly (Po0.05) throughout the observation period (Fig. 4).
In CET-treated monkeys, circulating INH A
concentrations were 82.970.46, 73.276.39 and
36.573.87 pg/mL at 0, 12 and 24 hr post treatment,
respectively. In 5.25% glucose-treated monkeys
(VEH for CET treatment), INH A concentrations
were 65.9714.8, 7174.0 and 6872.0 pg/mL at 0, 12
and 24 hr, respectively. The INH A concentrations
were significantly (Po0.05) lower 24 hr after CET
treatment compared with VEH treatment. Administration of exogenous rhLH 24 hr after CET treatment led to significant (Po0.05) increase in INH
A concentrations i.e. 62.075.2 pg/mL at 8 hr after
rhLH injection. However, administration of rhFSH
24 hr after CET treatment did not result in significant (P40.05) change in INH A concentration at
8 hr after injection. INH A concentrations were
32.476.8 and 30.874.8 pg/mL before and 8 hr after
rhFSH administration, respectively.
DISCUSSION
Expectedly, the patterns of gonadotropins and
ovarian hormones, excepting INH A throughout the
menstrual cycle in adult female bonnet monkeys,
appear strikingly similar to women [Vande Weile
et al., 1970] and the rhesus macaque [Knobil, 1974].
The INH A secretion patterns observed throughout
the luteal phase in this study is also similar to that
reported in women [Groome et al., 1996]. The
findings of simultaneous occurrence of mid cycle
peak E2 and LH surge concentrations are essentially
similar to that previously reported for the rhesus
macaque [Hotchkiss et al., 1971], but different from
the observation of occurrence of E2 peak surge
one day preceding the LH peak surge in women
[Vande Weile et al., 1970]. Although bonnet monkeys
Am. J. Primatol.
822 / Suresh and Medhamurthy
100
5
a
3
* ***
2
b
1
c c c
c
c
*
c
*
a
75
*
*
b
25
c
c
0.6
100
0.5
80
0.4
0.3
0.2
a
**
60
40
b
b
20
0.1
*
50
c
E2 (pg/ml)
FSH (ng/ml)
a
**
INH A (pg/ml)
P2 (ng/ml)
4
b
b
b b
b
b
0
24
48
72
96
120
0
24
48
72
96
120
L7
L8
L9
L10
L11
L12
L7
L8
L9
L10
L11
L12
Time (h) post CET treatment
Time (h) post CET treatment
Fig. 4. Circulating mean (7SEM) concentrations of P4 (top, right), INH A (top, left), FSH (bottom, right) and E2 (bottom, left) in
monkeys subjected to VEH (dotted line) or CET (150 mg/kg BW) treatment (solid line). Bars with different letters above them are
significant (Po0.05) from each other. Po0.05 when analyzed with student’s t-test in comparison to VEH- and CET-treated animals,
df 6 for each time points.
have been extensively used as surrogates for various
aspects of research related to humans, this is a first
study that provides comprehensive information on
patterns of secretions of gonadotropins and ovarian
hormones during the menstrual cycle in the bonnet
macaque. The FSH secretion data, especially the rise
in FSH secretion that occurs few days prior to the
onset of menses and on the day of menses, are very
similar to women [Lahlou et al., 1999].
Circulating INH A concentrations in bonnet
monkeys have not been reported earlier and this is
the first study that provides information on INH A
secretion throughout the menstrual cycle, especially
during the luteal phase. In addition to the wellcharacterized endocrine and paracrine actions of
ovarian inhibins, clinically they have also been
recognized as important biomarkers of conception
and as markers for early detection of reproductive
tissue tumors [Groome and Evans, 2000]. It is interesting to note that secretion of P4 peak 2–3 days
preceding the peak INH A secretion period, which is
also observed in Japanese macaques [Shimizu et al.,
2002]. The significance of occurrence of different time
peak secretions between P4 and INH A during the
luteal phase is not clear, but it may be that the
transcription and translation processes of INH A
require time for the ultimate expression of the protein
and/or its clearance as compared with simpler twostep enzymatic synthesis of P4 together with its very
short half-life. The physiological significance of
increased secretion of INH A by the CL and
subsequently by the placenta in the event of pregnancy is not clear. Understanding factors that
regulate INH A secretion during the luteal phase is
essential for examining its role in the development
Am. J. Primatol.
and function of CL during nonpregnant and pregnant
cycles. Systemic and intra-luteal administration of
INH A during mid luteal phase in rhesus monkeys
readily caused suppression of FSH without altering
the CL function [Stouffer et al., 1994]. It is of interest
to note here that mouse with INH-a gene knockout
has abnormal growth of CL and increased occurrence
of ovarian tumors, suggesting perhaps INH expression is essential for CL regression [Burns et al., 2003].
It is unique that CL appears to be the primary
site of synthesis of INH in primates [Bassetti et al.,
1990]. Expressions of INH a and INH bA subunits
have been reported in the CL [Eramaa et al., 1993;
Smith et al., 1991]. Several experiments were carried
out in this study to examine whether CL is the
primary source of INH A expression. First, lutectomy
resulted in precipitous fall in INH A levels. Second,
administration of GnRH receptor antagonist to mid
luteal phase monkeys caused fall in INH A concentration and third, administration of exogenous LH
but not exogenous FSH to monkeys subjected to
induced luteolysis resulted in restoration of INH A
concentration that also resulted in rescue of CL
function. Although it is well established that FSH
regulates secretion of both forms of INH, but in this
study, exogenous FSH treatment did not result in
elevated INH A concentrations. This finding is not
surprising, since it is well known that FSH receptor
expression becomes down regulated or undergoes extinction after ovulation and luteinization
[Minegishi et al., 1997]. We have observed low mRNA
expression of FSH receptor in the CL throughout the
luteal phase, and this may have contributed to lack of
response to exogenous FSH treatment and thus
absence of increase in INH A concentration.
Dynamics of Inhibin A and FSH Secretion / 823
The results from this study suggest an inverse
relationship between circulating INH A and FSH
concentrations during the luteal phase in the bonnet
monkey and inter-cycle rise in FSH during the lutealfollicular transition was observed after the significant
decline in circulating P4 and INH A concentrations.
These findings are similar to the previously reported
findings in women in which a gradual but significant
decline in circulating P4 and INH A concentrations
were observed prior to the FSH rise [Groome et al.,
1996; Roseff et al., 1989]. Before the onset of FSH rise
around the menstrual period, a gradual but significant decline in circulating P4 and INH A levels was
observed. It is clear therefore that the inter-cycle rise
in FSH starts during the late luteal phase as a result
of reduced negative feedback mechanisms responsible
for the suppression of pituitary FSH secretion.
Although it can be argued that the role played by P4
in the regulation of inter-cycle rise in FSH cannot be
ignored, however, P4 appears to mediate its action
mainly via its effect on the hypothalamic GnRH
secretion, where it is thought to reduce the frequency,
but increase the amplitude of LH pulse significantly
during the luteal phase of the cycle [Nippoldt et al.,
1989; Soules et al., 1984]. The decreased P4 level
during the late luteal phase of the bonnet monkey as
observed in this study, and as has been reported
previously [McCartney et al., 2002] increase frequency of GnRH pulses leading to perhaps increased
FSH secretion. However, it has been observed that
the increased frequency of GnRH pulses is not solely
responsible for inter-cycle rise in FSH in women
[Welt et al., 1997]. The rise in circulating activin A
concentration, a member of TGF-b super-family,
appears to be another molecule responsible for the
inter-cycle FSH rise [Muttukrishna et al., 2000].
To further gain insights into the mechanisms of
feedback regulation of pituitary FSH secretion by CL
during the luteal phase in the bonnet monkey,
lutectomy performed during mid luteal phase caused
a significant drop in the levels of circulating INH A
and P4 with a concomitant rise in FSH within
24–48 hr. It appears then that during the luteal phase,
the increased concentrations of INH A and P4 play an
important role in the maintenance of low FSH
secretion in the bonnet monkey. In women during
the mid luteal phase, following ovariectomy, a
significant drop in the levels of E2 and P4 was
observed within the first 24 hr but the concentrations
of FSH and LH increased gradually [Alexandris et al.,
1997]. On the contrary, our data did not show any
significant drop in the levels of E2 after lutectomy,
rather E2 levels appeared to rise after 24 hr postlutectomy. The findings that GnRH secretion appears
to be essential for maintaining basal FSH secretion
was further confirmed by the observation that
administration of GnRH receptor antagonist, CET,
did not result in alterations in FSH concentrations,
suggesting importance of GnRH secretion and INH A
in the control of pituitary FSH secretion during the
mid luteal phase of the bonnet monkey.
In summary, we have characterized endocrine
hormone profiles including INH A secretion throughout the menstrual cycle of the bonnet monkey. The
results from the experiments described in this study
suggest that INH A and P4 secreted during the luteal
phase regulate FSH secretion. The results also
suggest that increased GnRH secretion is essential
for the rise in FSH following withdrawal of inhibition
of regulation by P4 and INH A.
ACKNOWLEDGMENTS
We thank Dr. AF Parlow, NHPP for distribution
of monkey LH and FSH RIA kits. The staff of PRL is
gratefully acknowledged for their help with blood
sampling. Experimental protocols involving monkeys
in this study were approved by the institutional
animal ethics Committee of the Indian Institute of
Science. The experimental procedures followed are
based on guidelines formulated by INSA, IISc as well
as CPCSEA, India.
REFERENCES
Alexandris E, Milingos S, Kollios G, Seferiadis K, Lolis D,
Messinis IE. 1997. Changes in gonadotrophin response to
gonadotrophin releasing hormone in normal women following bilateral ovariectomy. Clin Endocrinol 47:721–726.
Bassetti AG, Winters SJ, Keeping HS, Zeleznik AJ. 1990.
Serum immunoreactive inhibin levels before and after
lutectomy in the cynomolgus monkey (Macaca fascicularis).
J Clin Endocrinol Metab 70:590–594.
Brannian JD, Stouffer RL, Molskness TA, Chandrasekher YA,
Sarkissian A, Dahl KD. 1992. Inhibin production by
macaque granulosa cells from pre and periovulatory
follicles: regulation by gonadotropins and prostaglandin
E2. Biol Reprod 46:451–457.
Burger HG. 1993. Evidence for a negative feedback role of
inhibin in follicle stimulating hormone regulation in
women. Hum Reprod 8:129–132.
Burns KH, Agno JE, Sicinski P, Matzuk MM. 2003. Cyclin D2
and p27 are tissue-specific regulators of tumorigenesis in
inhibin-á knockout mice. Mol Endocrinol 17:2053–2069.
De Jong FH. 1988. Inhibin. Physiol Rev 68:555–607.
de Kretser DM, Hedger MP, Loveland KL, Phillips DJ. 2002.
Inhibins, activins and follistatin in reproduction. Hum
Reprod Update 8:529–541.
Duffy DM, Stewart DR, Stouffer RL. 1999. Titrating luteinizing hormone replacement to sustain the structure and
function of the corpus luteum after gonadotropin-releasing
hormone antagonist treatment in rhesus monkeys. J Clin
Endocrinol Metab 84:342–349.
Eramaa M, Heikinheimo K, Tuuri T, Hildén K, Ritvos O.
1993. Inhibin/activin subunit mRNA expression in human
granulosa-luteal cells. Mol Cell Endocrinol 92:R15–R20.
Fraser HM, Robertson DM, deKretser DM. 1989. Immunoreactive inhibin concentrations in serum throughout the
menstrual cycle of the macaque: suppression of inhibin
during the luteal phase after treatment with an LHRH
antagonist. J Endocrinol 121:R9–R12.
Fraser HM, Lunn SF, Harrison DJ, Kerr JB. 1999. Luteal
regression in the primate: different forms of cell death
during natural and gonadotropin-releasing hormone
antagonist or prostaglandin analogue-induced luteolysis.
Biol Reprod 61:1468–1479.
Am. J. Primatol.
824 / Suresh and Medhamurthy
Groome NP, Evans LW. 2000. Does measurement of inhibin
have a clinical role? Ann Clin Biochem 37:419–431.
Groome NP, Illingworth PJ, O’Brien M, Pai R, Rodger FE,
Mather JP, McNeilly AS. 1996. Measurement of dimeric
inhibin B throughout the human menstrual cycle. J Clin
Endocrinol Metab 81:1401–1405.
Hotchkiss J, Atkinson LE, Knobil E. 1971. Time course of
serum estrogen and luteinizing hormone (LH) concentrations during the menstrual cycle of the rhesus monkey.
Endocrinology 89:177–183.
Knobil E. 1974. On the control of gonadotropin secretion in the
rhesus monkey. Recent Prog Horm Res 30:1–36.
Laven JS, Fauser BC. 2004. Inhibins and adult ovarian
function. Mol Cell Endocrinol 225:37–44.
Lahlou N, Chabbert-Buffet N, Christin-Maitre S, Le Nestour E,
Roger M, Bouchard P. 1999. Main inhibitor of follicle
stimulating hormone in the luteal–follicular transition:
inhibin A, oestradiol, or inhibin B? Hum Reprod
14:1190–1193.
Mather JP, Woodruff TK, Krummen LA. 1992. Paracrine
regulation of reproductive function by inhibin and activin.
Proc Soc Exp Biol Med 201:1–15.
Mather JP, Moore A, Li RH. 1997. Activins, inhibins and
follistatins: further thoughts on a growing family of
regulators. Proc Soc Exp Biol Med 215:209–222.
McCartney CR, Gingrich MB, Hu Y, Evans WS, Marshall JC.
2002. Hypothalamic regulation of cyclic ovulation: evidence
that the increase in gonadotropin-releasing hormone pulse
frequency during the follicular phase reflects the gradual
loss of the restraining effects of progesterone. J Clin
Endocrinol Metab 87:2194–2200.
Medhamurthy R, Priyanka G, Vinuthan MK, Manjunatha AM.
2007. Short term fasting leads to inhibition of responsiveness to LH- stimulated testosterone secretion in the adult
male bonnet monkey. Am J Primatol 69:791–801.
Minegishi T, Tano M, Igarashi M, Rokukawa S, Abe Y, Ibuki Y,
Miyamoto K. 1997. Expression of follicle stimulating hormone
receptor in human ovary. Eur J Clin Invest 27:469–474.
Muttukrishna S, Child T, Lockwood GM, Groome NP,
Barlow DH, Ledger WL. 2000. Serum concentrations of
dimeric inhibins, activin A, gonadotropins and ovarian
steroids during the menstrual cycle in older women. Hum
Reprod 15:549–556.
Nippoldt TB, Reame NE, Kelch RP, Marshall JC. 1989. The
roles of estradiol and progesterone in decreasing luteinizing
hormone pulse frequency in the luteal phase of the
menstrual cycle. J Clin Endocrinol Metab 69:67–76.
Plant TM, Medhamurthy R, Winters SJ, Gay VL. 1991.
Dynamics of the FSH-INHIBIN negative feedback loop in
the male rhesus monkey. 24th Annual Meeting of the
Society for the Study of Reproduction, Vancouver, Canada.
Abstract No. 140.
Priyanka S, Jayaram P, Sridaran R, Medhamurthy R. 2009.
Genome-wide gene expression analysis reveals a dynamic
interplay between luteotropic and luteolytic factors in the
Am. J. Primatol.
regulation of corpus luteum function in the bonnet monkey
(Macaca radiata). Endocrinology 150:1473–1484.
Roseff SJ, Bangah ML, Kettel LM, Vale W, Rivier J,
Burger HG, Yen SS. 1989. Dynamic changes in circulating
inhibin levels during the luteal follicular transition of the
human menstrual cycle. J Clin Endocrinol Metab 69:1033–1039.
Selvaraj N, Medhamurthy R, Ramachandra SG, Sairam MR,
Moudgal NR. 1996. Assessment of luteal rescue and desensitization of macaque corpus luteum brought about by
human chorionic gonadotrophin and de-glycosylated human
chorionic gonadotrophin treatment. J Biosci 21:497–510.
Shimizu K, Kojima C, Kondo M, Jin WZ, Ito M, Watanabe G,
Groome NP, Taya K. 2002. Circulating inhibin A and
inhibin B in normal menstrual cycle during breeding
seasons of Japanese monkeys. J Reprod Dev 48:355–361.
Smith KB, Millar MR, McNeilly AS, Illingworth PJ,
Fraser HM, Baird DT. 1991. Immunocytochemical localization of inhibin-a subunit in the human corpus luteum. J
Endocrinol 129:155–160.
Soules MR, Steiner RA, Clifton DK, Cohen NL, Aksel S,
Bremner WJ. 1984. Progesterone modulation of pulsatile
luteinizing hormone secretion in normal women. J Clin
Endocrinol Metab 58:378–383.
Stouffer RL, Dahl KD, Hess DL, Woodruff TK, Mather JP,
Molskness TA. 1994. Systemic and intraluteal infusion of
inhibin A or activin A in rhesus monkeys during the luteal
phase of the menstrual cycle. Biol Reprod 50:888–895.
Vande Wiele RL, Boqumil J, Dyrenfurth I, Ferin M,
Jewelewicz R, Warren M, Rizkallah T, Mikhail G. 1970.
Mechanisms regulating the menstrual cycle in women.
Recent Prog Horm Res 26:63–103.
Welt CK, Martin KA, Taylor AE, Lambert-Messerlian GM,
Crowley Jr WF, Smith JA, Schoenfeld DA, Hall JE. 1997.
Frequency modulation of follicle stimulating hormone
(FSH) during the luteal-follicular transition: evidence for
FSH control of inhibin B in normal women. J Clin
Endocrinol Metab 82:2645–2652.
Welt CK, Adams JM, Sluss PM, Hall JE. 1999. Inhibin A and
inhibin B responses to gonadotropin withdrawal depends on
stage of follicle development. J Clin Endocrinol Metab
84:2163–2169.
Yadav VK, Medhamurthy R. 2006. Dynamic changes in
mitogen-activated protein kinase (MAPK) activities in the
corpus luteum of the bonnet monkey (Macaca radiata)
during development, induced luteolysis, and stimulated
early pregnancy: a role for p38 MAPK in the regulation of
luteal function. Endocrinology 147:2018–2027.
Ying SY. 1988. Inhibins, activins, and follistatins: gonadal
proteins modulating the secretion of follicle stimulating
hormone. Endocr Rev 9:267–293.
Zeleznik AJ, Benyo DF. 1994. Control of follicular development, corpus luteum function and the recognition of
pregnancy in higher primates. In: Knobil E, Neill JD,
editors. The physiology of reproduction. New York: Raven
Press. p 751.
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