close

Вход

Забыли?

вход по аккаунту

?

The effect of reduced rate of growth on maturation of the male reproductive system of the albino rat.

код для вставкиСкачать
T H E E F F E C T O F REDUCED RATE O F GROWTH ON
JIATURATION O F T H E MALE REPRODUCTIVE
SYSTEJI O F T H E ALBINO R A T '
GEORGE B. TALBERT AND JAMES B. HAMILTON
Department of Anatomy, State Universit!] of New Y o r k College of
Xedicine at iVew Pork City, Brooklyn, N . P.
THREE FIGURES
The pioneer work of P. E. Smith ('26, '27) demonstrated
that secretions of the pituitary gland produce precocious maturation of the ovaries of the laboratory rat. Subsequently, the
role of the anterior lobe of the pituitary gland in effecting
such maturational changes in the testes and ovaries of different mammals has been studied extensively. The pituitary
glands of rats as young as 1 2 days of age are capable of
secreting gonadotrophin (Harris and Jacobsohn, '52). Since
the pituitary gland is able to secrete gonadotrophins, and the
gonads can respond to such stimulation, much earlier than
the age a t which maturation occurs normally, it seems apparent that maturatioii is controlled by still more antecedent
factors. The present data pertain t o the relationship in the
albino rat between body growth and maturation as judged
by the growth of the testes, semiiial vesicles, and ventral
prostate and by the initial appearance of spermatozoa in the
seminiferous tubules. The body growth was controlled by
quantitative restriction of the intake of food.
Many studies have been made on the effect of reduced caloric
intake upon the growth of the testes and other body organs
(Jackson, '15 ; Winters, Smith, illendel, '27 ; and Stewart,
This study is a by-product of work supported in p a r t by a research grant
(A-89) from the r a t i o n a l Institute f o r Arthritis aiid Metabolic Diseases, of the
National Institutes of Health, Public Health Service.
763
764
GEORGE B. TALBERT A K D J A M E S B. HAMILTOR
'16, '18). F o r the most p a r t these studies have involved such
severe dietary restriction that little or no growth mas perinitted f o r extended periods of time. In the present investigation the restricted animals were allowed to gain weight
a t a regular but reduced rate.
MATERIALS AS11 hIETHODS
The r a t s used in this study were all inales of T i s t a r stock
which were raised in our laboratory. In order to standardize
the weight at weaning, litters were reduced to '7 animals
within 48 hours after birth. Animals wei-e weaned at 20 days
of age and only those which weighed 43 to 49gm at 25 days
of age were included in the experiment.
The r a t s froni each litter which were within the above
weight range were separated into two groups. Growth of
of first group was made to conform to a standard curve
which had been established i n a preliminary experiment. This
curve extended from weaning until 57 days of age and v a s
based on the r a t e of growth of 25 male r a t s obtained from
6 litters, each containing 7 animals. During this period a
uniform rate of growth was maintained by slight restriction
in the amount of food made available to the faster growing
animals in the group. By this procedure a curve was derived
which can be followed by all our rats except those that g' row
at an especially slow rate.
In the second group the daily increment of growth was
reduced t o one-third of that in the first group by limiting
the food intake beginning at 25 days of age (fig. 1). These
curves were extrapolated a s a guide for controlling the
growth of the animals which exceeded 5'7 days of age.
The r a t s were weighed daily arid were given their food
ration at approximately the same time each day. No animal
was fed less than 5 g m of food per day. The aiiiinals were
kept i n a room maintained at 25°C. ivith 30% relative humidity. By adherence to these procedures all the r a t s were
* Obtained f r o m Carworth Farms.
REDUCED G R O W TH A N D MATURATION
765
maintained within three gm of the desired weight throughout
the period of study.
The animals were autopsied at two t o 5 day intervals as
indicated in figures 2 and 3. At autopsy the testes, seminal
vesicles, and ventral prostate, along with other organs which
are not included in this report, were stripped of grossly
visible fat and weighed on a torsion balance. Fluid was re-
AGE IN DAYS
Fig. 1 Growth curves of rats with normal and quantitatively-restricted food
intake.
moved from the seminal vesicles prior t o weighing. A
representative series of organs were fixed for histological
study and stained with hematosylin and eosin. The seminiferous tubules of the testes were examined f o r the presence
of spermatozoa.
RESULTS
Growth of the testes, seminal vesicles, and ventral prostate
is graphed separately in relation to (1) age and ( 2 ) body
766
GEORGE R. TALBERT A B D JAMES B. HAMILTON
weight. Weights of these organs in the growth-retarded
animals autopsied a t 76 and 96 days of age are not included
in figures 2 and 3 where organ weight is plotted against age
because data were not obtained at comparable ages in the
standard group.
Testis. I n absolute terms the rate of testicular growth
was decreased considerably by reduction in the rate of growth
of the body (fig. 2). Relative to body weight, however, the
testes of the animals on a restricted diet were larger than
those of control animals with the same body weight until a body
weight of 150gm was attained. Testicular weight is related
to both age and body weight during the period of maturation
(fig. 2).
Histological study showed that spermatozoa appeared initially in the lumen of the seminiferous tubules at 32 to
35 days of age in both the restricted and control groups.
At this age the body weights of the animals were 55 to GO p i
in the restricted group and 76 to 90gm in the control group
whereas the testes weighed 500 to G50mg in the restricted
group and 575 to 875 mg in the control group (figs. 1 and 2 ) .
At successively older ages the quantity of spermatozoa
in the seminiferous tubules appeared t o increase at the same
rate in spite of the fact that the testes weight and body weight
of the two groups became increasingly divergent (figs. 1
and 2).
Under the conditions of this experiment the maturation
of spermatozoa in this species is closely related to the age of
the animal. Testis weight cannot be used as an accurate index
of the maturational status of the spermatozoa and body weight
is even less closely related.
Seminal vesicles and ventral prostate. Reduction of the
rate of body growth markedly delayed the growth of the
seminal vesicles and ventral prostate after 40 days of age
(fig. 3). The period of rapid maturational growth which occurs at this time in the control animals did not appear until
after 55 days of age in the group with restriction of food.
767
REDUCED GROWTH AND MATURATION
h
%
P
0
Y
3
.
i
*
Y
.OQ
4
-3
0 - 0 4 0
0
I.
0
s
0
0
0
R)
0
0
0
0
8
N
SWVUOllllN
NI
0
0
0
1H9l3M SllS31
8
Y)
-8
te
i;;g
.
Y
3
768
t
GEORGE B. TALBERT A N D J A M E S B. H A M I L T O N
O--RESTRICTa)
b--STANDARD
o --RESTRICTED
A --STANDARD
2001
200 o--RESTRICTED
0--RESTRICTED
b--STANDARD
A --STANDARD
2 160E
t
-1
s
5 IZO-
4
.
1
Jo
36
40
AGE
4 4
45
50
IN DAYS
I ++I4
4ii
0
b
4 4
4
55
60
6!
50
75
100
125
/50 175
BODY WEIGHT IN GRAMS
200
2f5
Fig. 3 Change i n weight of the ventral prostate and seminal vesicles of rats with normal
and restricted food intake in relation to age and body weight. Vertical lines indicate standard
error of the mean.
REDUCED GROTVTII A N D M A T U R A T I O N
769
Relative to body weight, these organs were larger in dieted
than in control rats after a body weight of 100gm was attained. I n this connection it should be appreciated that the
dieted animals mere older than the control animals by the
time they had attained the same body weight.
The similarity in rates of growth between prostate and
seminal vesicles in dieted animals (fig. 3) is noteworthy
because the threshold for responsiveness to androgens is lower
in the prostate than in the seminal vesicles (Callow and
Deansley, '35; Moore and Price, '38) and in normal animals
there is a rapid increase in rate of growth in the prostate
before a similar increase occurs in the seminal vesicles. That
prostate and seminal vesicles mature at the same slow rate
upon restriction of food is open to several interpretations,
one of which is that testicular secretions are not maintained
for any noticeable length of time at levels that stimulate more
rapid growth of the prostate than of the seminal vesicles.
DISCUSSION
Restriction of food t o the extent that the increase in body
weight of meanling rats proceeded at only one-third that of
the control animals resulted in retarded maturation of secondary sex organs. It did not eliminate stimulation of these
organs nor delay the maturation of sperniatozoa in the seminiferous tubules ; both of these phenomena occur in severe
inanition (Stone, '24).
Possible explanations of the failure t o delay the initial
appearance of spermatozoa are that spermatogenesis (1)
was initiated before the diet was restricted and ( 2 ) is relatively resistant t o a moderate reduction in food intake. There
is evidence that spermatogenesis in the rat begins prior to
the age when the diet of our animals was restricted. The time
required for spermatogenesis in the rat is estimated to be
16 days (Roosen-Runge, '51), 20 days (Leblond and Clermont,
'52) and 26 days (Shaver and Mason, '50). An estimate of 20
days would place the initiation of sperniatogenesis at no later
770
GEORGE B. TALBERT A S D J A M E S B. HAMILTON
than 15 days in these rats. The supply of food was not
restricted until the animals were 25 days old.
At present it is not possible to define the mechanisms by
which restriction of food delays the age at which secondary
sex organs become mature. Many possibilities exist, including
the following factors which are known to influence maturation :
1. Lack of foodstuffs necessary f o r growth of the secondary sex organs.
2. Effect of reduced supply of foodstuffs upon the production of gonadotrophins and androgens and perhaps
upon centers in the nervous system which control the
pituitary gland.
3. The mass of the body (van Wagenen, '49).
4. The amount of depot fat (Bruch, '39; Reynolds, '46).
5. Adrenocortical secretions (Wilkins and Cara, '54 ; Richter and Uhlenhuth, '54).
Whereas growth of most non-reproductive organs is dependent primarily on the amount of food utilizable for growth,
the reproductive organs are dependent not only on the availability of food but also on the quantity and quality of hormones necessary for stimulation of their growth. I n severe
inanition, secretion of gonadotrophins appears t o be reduced
(lllulinos and Pomerantz, '41 ; Jlason and Wolfe, '30 ; Meites
and Reed, '49). If the amount of gonadotrophin is decreased
by the degree of dieting in our series of animals this reduction
was not severe enough to delay significantly the appearance
of mature spermatozoa.
The decreased rate of growth of seminal vesicles and prostate is probably produced by a failure of androgenic stimulation. Reduced androgenic stimulation appears t o be the
indirect result of reduced stimulation of the testes. Such an
effect has been clearly demonstrated in adult rats subjected
to severe inanition. The secondary sex organs retain responsiveness t o androgens even in states of severe starvation
(Xoore and Samuels, '31 ; illulinos and Pomerantz, '41).
REDUCED G R O W T H A N D M A T U R A T I O N
771
Body size (weight and length) can be a decisive factor in
retardation and acceleration of the onset of maturation (Hildebrand, '32; Engle et al., ' 3 7 ; Bogart and associates, '40;
van Wagenen, '49). Whether the influence of body weight
upon the initiation and completion of maturation is due to
size and function of the lean mass, of the amount of body
fat, or both is not clear. It is known that fat individuals
mature precociously (Bruch, '39; Reynolds, '46) and that increments in depot fat are significantly correlated with augmented titers of ketosteroids and androgens (Hamilton, '54)
during certain periods of the lifespan.
SUMMARY
A study was made in male albino rats o n the effect of body
growth on the age at maturation. By restriction of the amount
of food, beginning at 25 days of age, the growth rate
of the body was reduced to one-third of that of control rats
allowed to eat almost nd libitum. The absolute rate of growth
of testes, seminal vesicles, and ventral prostate was also
reduced although all three organs were considerably larger
than in control animals of the same body weight. Spermatozoa
appeared initially in the seminiferous tubules at the same age
in dieted and control groups. It is concluded that reduction in
growth, as regulated by restriction of food to the extent and at
the ages employed in this experiment, slowed the completion of
maturation of the secondary sex organs, but did not delay
the initial appearance of spermatozoa in the seminiferous
tubules.
I n the animals with restricted intake of food the rate of
maturation became similar in both prostate and seminal
vesicles. This is in contrast to the more rapid growth of the
prostate than the seminal vesicles in control animals and
seems noteworthy in view of the lower threshold of response
to androgens that characterizes the prostate.
772
GEORGE B. TBLBERT A N D J A M E S B. HAMILTON
L I T E R A T U R E CITED
GOGART, R., G. S P E R L I S G , L. EaRXES AND s. ASDELL 1940 The influence of
reproductive coiitlition upon growth in the f cniale rat. Am. .J. Physiol.,
I?&: 335-371.
E R U C H , H. 1939 Obesity in childhood. I Physical gron tli and development
in obese children. Am. J. Dis. Child., 58: 457-484.
C 4 L L O W , R. K., AND R. DE~XESLY 1935 Effect of androsterone aiid of male
hoimoiie concentretes on accessory reproductive organs of castrated
rats, niice and gniiica pigs. Biochem. J., 3: 1424.1445.
ENGLE,E., R. CRAFTS AND C. ZEITHAML 1937-3s First estrus in rats in
relation to age, weight, and length. Proc. Soc. Exp. Biol. and bled.,
3 7 : 437-432.
€1 IMILTOS, J . B. 1934 Androgenic activity per milligram of calorimetrically
me:rsured ketostvroids in urine : an index of coiitributioiis from testiculnr and extra-testicular sourceb. J. Cliii., Endoerinol. and Metals.,
11: 433-471.
IIIRBIS, G. W., AND D. JACOBSOIIN
1952 Functional grafts of the anterior
pituitary gland. Proc. Roy. Soc., London, s. B., 1 3 9 : 263-276.
I~ILDEBRAND,
S . 1932 Growth of diamond-back terrapins : size attained, sex
ratio, aiid longevity. Zoologiea, 9 : 551-563.
J ICKSON, C. M. 1915 Changes in the relative weights of the various parts,
systems, and oigans of young albino rats held at constant body weight
by underfeeding f o r various peiiods. J. Exp. Zool., 1 9 : 99-156.
L r m o N D , C’. P., AND Y . CLERLIONT1952 Spermiogenesis of rat, mouse, harmster
aiid guinea pig as revealed by tlie periodic acid-fuchsin sulfurous
acid technique. Am. J. Anat., 90: 167-216.
M-\sos, K. E., -4ND J. I f . WOLFE 1930 The physiological activity of 1iypoph)ses
of rats uiider vaiioiis experimeiital conditions. Anat. Rec., 45: 232
(ah.).
MEITES,J., AXD J. 0. REED 1949 Effects of restricted feed intake in intact and
ovariectouiized r a t s on pituitary lactogen and gonadotrophin. Proc.
Soc. E Y ~Biol.
.
and Med., 70: 513-516.
~ I O O R E , C. R., BXD L. T. s 4 M U E L S 1931 Tlic action of testis hormone in
correcting changes induced in tlie rat prostate and seminal vesicles
b y vitamin E deficieiicy or partial inanition. Am. J. Physiol., 96:
278-288.
1941 The reproductive organs in malXiuLIsos, N. G., A N D L. POMERAXTZ
nutrition. Effrcli of cliorionic gonadotrophin upon atrophic genitalia of
uiiderfed male rats. Endocrinology, &9: 267-275.
REITOLDS, E. L. 1946 Sexual maturation and the growth of f a t , muscle, and
bone in girls. Child Develop., 1 7 : 121-144.
RICHTER,C., AND E. UHLENIIUTH, 1954 Conipnrison of the effects of gonadectomy on spontaneous activity of wild and domesticated Norway rats.
Endocrinology, 54 : 311-322.
ROOSEN-RUNGE,
E. C. 1951 Quantitative studies on sperniatogenesis in the
albino rat. 11. Tlic duration of spermatogenesis and some effects of
colchicine. Am. J. Anat., S8: 163-176.
REDIJCED G R O W T H A N D M A T U R A T I O N
773
SHAVER,
S. S., AND K. E. MASON 1950 Selective testicular damage in rats duc
t o X rags. Anat. Ree., 106: 246 (abs.).
SMITH,P. E. 1926 Hastening development of female genital system b y daily
homoplastic pituitary transplants. Proc. Soe. Esp. Bid. and &led.,
24: 131-132.
SMITH,P. E., AND E. T. ENGLE1927 Experimental evidence regarding the
role of the anterior pituitary i n the development and regulatioii of
the genital systeiii. Am. J. Anat., 4 0 : 159-217.
STEWART,
C. A. 1916 Growth of the body and of the various organs of young
alhiiio rats after iilaiiition f o r various periods. Biol. Bull., 31 : 16-51.
1918 Changes i n the relative weights of the various parts, systems
and organs of young albino rats underfed f o r various periods. J.
Esp. Zool., 25: 301-353.
STONE,C. P. 1924 Delay i n the awakening of copulatory ability i n the male
albino r a t incurred by defective diets. I Quantitative deficiency. J.
Comp. Psychol., 4 : 195-224.
VAN WAGEEEN,G. 1949 Accelerated growth with sexual precocity in female
monkeys receiving testosterone propionate. Endocrinology, 45: 544.
WILKINS,L., BND J. CARA 1954 Further studies on treatment of congenital
adreiial hyperplasia with cortisone. V Effects of cortisone on testicular development. J. Clin. Endocrinol. and Metab., 1 4 : 287-296. II
WINTERS,J. C., A. H. SNITII, AND L. B. MENDEL 1927 The effects of dieting
deficiencies on the growth of certain body systems and organs. Am.
J. Physiol., 80: 576-593.
Документ
Категория
Без категории
Просмотров
2
Размер файла
533 Кб
Теги
albina, effect, growth, malen, rate, maturation, rat, system, reduced, reproduction
1/--страниц
Пожаловаться на содержимое документа