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Effects of Human Chorionic Gonadotropin, Prolactin,
and Bromocriptine on Photoperiod-induced Testicular
Regression and Recrudescence in Golden Hamsters
A. BARTKE, M. P. HOGAN, AND G. B. CUTTY
From the Department of Obstetrics and
Gynecology, The University of Texas
Health Science Center at San Antonio,
San Antonio, Texas
Exposure of adult male hamsters to short
day-length (short photoperiod) causes atrophy
of their reproductive systems. Hamsters were
transferred from long to short photoperiod and,
starting two months later, injected three times a
week for three weeks with saline, 1.25, 5, or 20
IU of human chorionic gonadotropin (hCG).
Treatment with 5 or 20 IU hCG resulted in significant increases in the weights of the testes
and the seminal vesicles. In another group of
animals, identical doses of hCG were injected
starting at the time of transfer from long to
short photoperiod. After 14 weeks of treatment,
testicular weight was significantly greater in
animals given 20 IU hCG than In animals injected with saline, although it approximated
only 50% of testicular weight in adult males
kept in long photoperiod. Since we have previously obtained very similar results using prolactin
(PRL) producing ectopic pituitary homografts,
it was of interest to examine the interaction
of pituitary grafts and hCG. Male hamsters
were transferred to a short photoperiod and
treated with a transplant of one pituitary from
an adult female hamster plus 5 IU hCG three
times a week or with hCG alone. After 15 weeks,
the weights of the testes and the seminal vesicles were significantly greater in grafted hCG-treated hamsters than in those animals treated
with hCG only. Testicular weight in animals
given both grafts and hCG corresponded to approximately 75% of testicular weight in long
photoperiod controls, while seminal vesicle
weights in these two groups did not differ. To examine the role of endogenous PRL in
long photoperiod-induced testicular recrudescence, hamsters which had been exposed to a
short photoperiod for two months were returned to a long photoperiod and treated daily
with bromocriptine (Sandoz CB-154, an inhibitor
of PRL release) or with vehicle. After three
weeks, the weights of the testes and the seminal vesicles were significantly lower in
bromocriptine-treated than in control hamsters,
but after five and a half weeks these differences were no longer evident. We conclude that (1) suppression of the release of both PRL and gonadotropins is responsible for gonadal regression in short
photoperiod, and (2) stimulation of PRL secretion contributes to recrudescence of the male
reproductive system in long photoperiod.
Key words: prolactin, gonadotropins, hamsters, testicular regression, pituitary homografts
Submitted on July 12, 1979
Revised on October 12, 1979
Accepted on October 15, 1979
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