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Observations on the adrenal glands of the mongoose.

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Observations on the Adrenal Glands of the Mongoose
STURGIS McKEEVER AND P. QUENTIN TOMICH
Department of Zoology, University of California, Davis and
Plague Research Unit, State Department of Health,
Honokaa, Hawaii
ABSTRACT
Adrenal glands from mongooses, classified according to sex, age and
reproductive condition, were examined histologically. The capsule, cortical zones and
medulla were described and differences exhibited by the various classes were noted.
Percentage width of the three cortical zones was computed for the different classes.
Similarity in relative weights of glands from animals classified according to age and
reproductive condition, as reported in the literature, was reflected in similarity of the
histological appearance of glands from animals so classified. Sexual dimorphism in
relative weight of adrenals from adult animals was found to be attributable to development of a distinct inner zona fasciculata in adult females. Glands of adults of both
sexes were characterized by presence of much connective tissue a t the reticularismedulla border. High adrenal weight/body weight ratio in fetuses was attributable to
a high degree of vascularization and to presence of many large vacuoles in the cytoplasm of lfascicular cells.
Adrenal glands of wild carnivores have
received limited attention compared with
those of rodents. Population studies of the
small Indian mongoose, Herpestes auropunctatus, related to the plague problem
in Hamakua District, Hawaii have permitted studies on adrenal size of this
carnivore (Tomich, M S ) . Glands were
grouped according to sex, age, reproductive condition, and weight of the animals; and adrenal size was expressed in
milligrams per 100 gm body weight
(mg % ). Average weight of adrenals from
adult males (26 mg % ) was significantly
less (P < 0.01) than that of adrenals from
adult females (51 mg % ). Weights of
adrenals from immature males (35 mg % )
and immature females (38 mg % ) were
also significantly different (P < 0.05) and
there was a significant difference between
weights of glands from juvenile and adult
animals of the same and opposite sexes
( P < 0.01). Among the three classes of
reproductively active females, adrenal size
of those in lactation was significantly
larger than those in the preimplantation
or pregnant stages ( P < 0.05). Adrenals
of the latter two classes did not differ in
size from those of inactive females or from
each other. Adrenal weight decreased as
body weight increased in both reproductively active and inactive animals of both
sexes, but the differences between con-
secutive weight classes were not significant. Weight of adrenal glands from nearterm fetuses (125 mg % ) was significantly
greater ( P < 0.01) than that of glands
from juvenile or adult animals.
This paper reports the results of a supporting study of the histology of adrenal
glands of representative animals from the
sex, age and reproductive classes of the
above study, with additional material from
South Kona District.
METHODS
All animals were collected on the island
of Hawaii. Adrenals were removed from
freshly-killed, and in a few instances,
frozen animals and fixed in either 10%
neutral formalin or Bouin’s fixative. The
glands were later embedded in paraffin,
sectioned at 7 c1 and stained with Pasini’s
stain. Measurements of the cortical zones
were made with an ocular micrometer at
70 X .
A difference between compared values
was considered to be statistically significant when P A 0.05.
OBSERVATIONS
Widths of the three zones of the adrenal
cortex, expressed as per cent of the total
1 This research was supported jointly by the University of California, the State of Hawaii Department of Health and by National Institutes of Health
Grant E-2886, Charles M. Wheeler, Principal Investigator.
163
STURGIS McKEEVER AND P. QUENTIN TOMICH
164
7
6
5
:4
a
u
1
3
2
1
+-+
40
50
60
70
80
PERCENT
Fig. 1 Width of the three zones of the adrenal cortex, expressed as a percentage of the
total width of the cortex, for Herpestes auropunctatus, classified according to sex, age, and
reproductive condition. The classes, and sample size of each, were: class 1, sexually active
males, 12; class 2, juvenile males, 4; class 3, sexually active females, prepregnant, 4;class 4,
pregnant, 11; class 5, lactating, 8; class 6, adult females, non-active, 8; class 7, juvenile
females, 3. The median vertical bar represents the mean, the shaded area represents two
standard errors, and the horizontal line represents the extremes.
10
20
30
width of the radius of the cortex, are presented for seven classes of animals in
figure 1. There was no significant difference in width of either the fasciculata or
reticularis among the various classes. In
all classes except pregnant females and
juvenile females, the fasciculata was significantly wider than the reticularis. Average width of the glomerulosa was less than
10% of the total width of the entire corex
in dl classes except juvenile females,
where there was great variability in width
of the cortical zones of the three specimens
examined.
The adrenal gland was surrounded by
a capsule consisting of dense connective
tissue throughout, except in juvenile animals where there was an inner cellular
layer. Thin strands of connective tissue
extended from the capsule between the
columns of cells in the cortex (fig. 3 ) .
The zona glomerulosa consisted of radially arranged columns, usually of two rows
of alternately arranged cells. Capsular
ends of two columns frequently were connected by an arch. The capsule-glomerulosa border was distinct, but the transition
between glomerulosa and fasciculata was
poorly differentiated. The glomerulosa
could be distinguished by cells which were
more densely packed, and by nuclei which
were smaller and more densely stained,
than those of the fasciculata (fig. 3 ) .
The zona fasciculata consisted of poorly
defined and broken columns of single rows
of cells or, more frequently, of double rows
of cells alternately arranged. Cells were
cuboidal or slightly columnar, with the
long axis at right angles to the radius of
the gland. Fascicular cells were larger in
male than in female glands (figs. 4-5).
165
MONGOOSE ADRENAL GLANDS
In adrenals of adult females, the fasciculata consisted of the normal outer zone
and a distinctive inner zone. The inner
zone, though present in all adult females,
was most pronounced in those which were
sexually active; in the latter group the
inner zone constituted half or more of the
total width of the cortex. This zone was
characterized by enlarged cells which were
arranged in more distinct columns than
those of the outer fasciculata, enlarged
sinusoids between the columns of cells,
and very dense acidophilic cyptoplasm.
Cells of the outer fasciculata contained
many fine vacuoles, and the cytoplasm was
slightly basophilic, so that the difference
between the inner and outer zones was
readily apparent (fig. 5).
When measurements of juvenile glands
of both sexes were combined and compared with measurements of adult male
and all adult female glands, the percent-
1-
I
GLOME R ULOSA
age width of the fasciculata and reticularis did not differ among the three classes;
but the width of the glomerulosa of adult
females was significantly less than that of
of adult males or juveniles (fig. 2 ) . In
actual width, however, the fasciculata of
adult females was 26% greater than that
or adult males; but actual width of the
glomerulosa and reticularis did not vary
significantly among the three classes. Thus,
the greater size of adrenals from adult
females was correlated with enlargement
of the zona fasciculata through formation
of an inner fasciculata. A correlation between maximum average width of the
fasciculata and maximum average weight
of the adrenal was also evident in lactating
females (fig. 1 ) .
The reticularis consisted of cuboid or
ovoid cells arranged in a broken network
and interspersed with sinusoids of varying
size. In some specimens the cells were
mm F A S C I CU L ATA
m R E T ICUL A R I S
J *
0
* +-e=&z
I-
II
-10
20
30
40
PERCENT
50
60
70
Fig. 2 Width of the three zones of the adrenal cortex expressed as a percentage of the
total width of the cortex (lower figure), and the actual width, in microns (upper figure),
for Herpestes auropunctatus. Classes, and sample size of each, were: class 1, adult males,
12; class 2, adult females, 32; class 3, juveniles of both sexes, 7. The median vertical bar
represents the mean, the shaded area represents two standard errors, and the horizontal
line represents the extremes.
166
STURGIS McKEEVER AND P. QUENTIN TOMICH
very compact and sinusoids were small,
while in others the cells were widely spaced
among greatly enlarged sinusoids (figs.
6-7). There was considerable variation
of this characteristic among animals of
the same class.
Connective tissue was present in varying
amounts in the inner reticularis of adrenals from adults. In some glands, connective tissue was present to such a degree
that reticular cells occurred only as isolated individuals (fig. 6 ) . Juvenile glands
contained little or no connective tissue at
the reticularis-medulla border.
Medullary cells were irregularly arranged in irregular groups of two-ten cells.
The groups were surrounded by thin
strands of connective tissue. The cytoplasm was sparse, and cell membranes
were indistinguishable in all specimens
(fig. 7 ) .
Adrenal glands of three near-term fetuses
were examined. The zona glomerulosa was
well delineated. The remainder of the
gland consisted mainly of fascicular cells
which were in poorly aligned columns or
were non-aligned. The cells were large and
contained many large vacuoles in an otherwise dense cytoplasm. The partial columns
were well separated by large sinusoids
(fig. 8). Scattered or coalesced islands of
medullary tissue occurred near the center
of the gland.
Seven of the 51 specimens were taken
in Kona District and were much fatter than
those taken on the main study area. However, there was no discernible histological
difference in glands of animals from different areas but of the same class.
DISCUSSION
Variations in weight of adrenal glands
of mongooses classed according to age,
sex and reproductive activity (Tomich,
MS), were reflected in the histological
appearance of the gland. Thus, relative
weight of the glands from adult females is
greater than that of glands from adult
males, a phenomenon of common occurrence in many eutherians (Chester Jones,
'57; Christian, '52). Histological examination demonstrated that this sexual dimorphism in the mongoose is attributable
to development of a pronounced inner zona
fasciculata in adult females, a zone not
present in males or juvenile animals.
Chester Jones ('57) defined the inner
zona fasciculata, but made no mention of
whether it was present in all species of
mammals. A summary of the results of
histological studies of three species of
rodents is, therefore, pertinent. Hypertrophy of the adrenal cortex of sexually
active female Microtus montanus was associated with enlargement of both the fasciculata and reticularis, with the major
hypertrophy in the fasciculata (McKeever,
'59). The fasciculata was not differentiated into two sub-zones. In Citellus beldingi the females had larger adrenals than
males, and among sexually active females
the adrenals were largest in lactating animals, just as in the mongoose (McKeever,
' 6 3 ) . In Citellus, however, the fasciculata
had a greater relative width in sexually
non-active than in active animals; and a
greater width in pregnant than in lactating
animals. Enlargement of the reticularis
during the breeding season, with formation of an outer sub-zone, has been reported for C. tridecemlineatus (Zalesky,
'34). In neither species of Citellus was
there formation of two sub-zones of the
fasciculata such as was characteristic of
adult female mongooses.
The greater relative size of adrenals
from near-term fetuses, compared with
those from juvenile and adult mongooses,
may be attributed to a larger vascular
supply and vacuolization of fascicular cells
in the embryonic gland.
LITERATURE CITED
Chester Jones, I. 1957 The Adrenal Cortex.
Cambridge Univ. Press, Cambridge, pp. 9-10;
16-17.
Christian, J. J. 1952 The relation of adrenal
weight to body weight in mammals. Naval
Med. Res. Ins. Memo. Rep., 52-7: 941-946.
McKeever, S. 1959 Effects of reproductive activity on the weight of adrenal glands in Microtus montanus. Anat. Rec., 135: 1-5.
1963 Seasonal changes in body weight,
reproductive organs, pituitary, adrenal glands,
thyroid gland, and spleen of the Belding ground
squirrel (Citellus beldingi). Amer. J . Anat.,
113: 153-173.
Tomich, P. Q. Weight variation in adrenal
glands of the mongoose in Hawaii. MS.
Zalesky, M. 1934 A study of the seasonal
changes in the adrenal glands of the thirteenlined ground squirrel (Citelks tridecemlineatus) with particular reference to the sexual
cycle. Anat. Rec., 60: 291-321.
PLATE
PLATE 1
EXPLANATION O F FIGURES
3
Connective tissue capsule with strands of connective tissue extending
into the cortex below. Small cells of the glomerulosa in central area
contrast with large cells of the fasciculata below. Pasini. x 300.
4 Cells of the zona fasciculata of a sexually active male showing larger
size of the cells compared with those of a n adult female in figure 5.
Pasini. x 300.
168
5
Cells of the zona fasciculata of a lactating female showing the outer
fasciculata in the lower half of the figure and the inner fasciculata
in the upper half. Note the dense cytoplasm and enlarged sinusoids
in the inner fasciculata. Pasini. X 300.
6
Inner portion of the reticularis of a lactating female showing abundance of connective tissue and pyknotic nuclei of scattered reticular
cells. Pasini. X 300.
7
Inner portion of the reticularis of a sexually active male in upper
two-thirds of figure showing absence of connective tissue, large
sinusoids and abundance of reticular cells. Medulla in lower third
of figure showing absence of definite cell boundaries. Pasini. X 300.
8
Adrenal of a 19.8-gm, near-term fetus showing large and abundant
sinusoids, abundance of vacuoles i n fasicular cells and scattered
islands of medullary cells near bottom of figure. Pasini. X 75.
MONGOOSE ADRENAL GLANDS
Sturgis McKeever and P. Quentin Tomich
PLATE 1
169
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