Developmental Changes in Testicular Function and Inhibin Secretion of Golden Hamsters (<i>Mesocricetus auratus</i>)

Abstract

Abstract. We studied developmental reproduction of male golden hamsters (Mesocricetus auratus) by determining hormone secretion, observing morphological changes including distribution of immunoexpression of inhibin α subunit, 3β-hydroxysteroid dehydrogenase (HSD), and investigating sperm head count from birth to adulthood. Immunoexpression of inhibin α subunit was found in interstitial cells of not well organized testes of neonatal animals, and positive staining was also found in Sertoli cells in developing animals. However, the intensity of immunostaining in Sertoli cells varied when the spematogenic cycle of the seminiferous epithelium began. Testosterone levels in the plasma and testicular contents of testosterone and immunoreactive (ir)-inhibin increased from around 25 days of age, about 10 days before the presence of the first sperm in the testis. On the other hand, plasma concentrations of ir-inhibin progressively increased from birth to 10 days of age, when it reached peak levels. A reciprocal pattern of change between plasma concentrations of ir-inhibin and FSH was found from 10 days of age. Plasma concentrations and pituitary contents of LH increased from 15 days of age and reached adult levels about 40 days of age. The present results suggest that inhibin is an important factor in the regulation of FSH secretion even in infant male golden hamsters, and the regulated FSH may control the increasing the number of germ cells. Inhibin might be not the only endocrine factor as the regulator of FSH secretion, but also a paracrine or autocrine factor which is involved in spermatogenesis in the golden hamster. Key words: Inhibin, Hamster, Development, Testis (J. Reprod. Dev. 48: [343][344][345][346][347][348][349][350][351][352][353] 2002) arly 20 th century experiments, which were the initial proposal for the existence of inhibin, showed that destruction of the germinal epithelium by irradiation caused hyperfunction in the absence of atrophy of the second sex glands [1], and that injection of aqueous testicular extracts to castrated rats prevented the appearance of enlarged "castration cells" in the pituitary [2,3]. These

Inhibin Secretion in the Golden Hamster (Mesocricetus auratus) Testis During Active and Inactive States of Spermatogenesis Induced by the Restriction of Photoperiod.

“…FSH is a potent stimulator of inhibin production [1]. Plasma concentrations of FSH in the premature hamster are relatively high, and the levels are almost equal to those of sexually mature animals [3,21]. In contrast to premature animals, FSH levels found in sexually inactive animals, induced by exposure to short photoperiod in the present study, were clearly lower than those in sexually active mature males.…”

“…We used the method of immunoneutralization against endogenous inhibin and this is one of good model fo r demonstrating that inhibin ha s a physiological role in the regulatio n of FSH secretion. We also demonstrated the changing pattern of plasma concentrations of FSH and inhibin during development in male hamsters [3]. We found a reciprocal changing pattern between plasma concentrations of FSH and inhibin, and we concluded that inhibin in developing male golden hamsters controlled FSH secretion.…”

“…However, the present immunostaining results showed only partial similarity between those testes. Although testes looked morphologically similar to p r e m a t u r e te s te s , th e d i s tr i b u t i o n o f immunostaining of inhibin α subunit in Sertoli cells and Leydig cells in the animals exposed to the short pho t o perio d wer e di ffer ent fro m t ho se i n developing animals as described previously [3]. In the developing hamster, before the start of the spermatogenic cycle, the intensity of inhibin α subunit in each seminiferous tubule was uniform, and most of Leydig cells showed strong positive staining for inhibin α subunit.…”