Maintenance of Advanced Spermatogenic Cells in the Adult Rat Testis: Quantitative Relationship to Testosterone Concentration within the Testis*

Abstract

The studies described herein were designed to examine whether there is a threshold concentration of testosterone (T) within the seminiferous tubules that is required to maintain spermatogenesis in the rat, or alternatively, whether there is a dose-response relationship between the intratesticular T concentration and the maintenance of spermatogenesis. T was administered to intact adult male rats via sustained release polydimethylsiloxane capsules in order to experimentally clamp T at well defined concentrations within the seminiferous tubules. Implantation of T-filled capsules of increasing sizes resulted in linear increases in T concentrations in serum, interstitial fluid, and seminiferous tubule fluid (STF). We examined the effect of step decreases in intratesticular T concentration on the numbers of advanced spermatogenic cells maintained by the testis over a 2-month period. Quantitatively complete spermatogenesis was maintained despite an 80% reduction in the STF T concentration (to approximately 13 ng/ml) from control values. The ability of the testis to maintain complete spermatogenesis was extremely sensitive to further decreases in STF T concentration. Thus, reduction of the STF T concentration from approximately 13 to 9 ng/ml resulted in a reduction in the number of advanced spermatids that were maintained in the testis by approximately 100 x 10(6). Reduction of the STF T concentration to approximately 4 ng/ml resulted in a further reduction in the number of advanced spermatids per testis by 100 x 10(6). Taken together, these data support the contention that there is far more T present within the seminiferous tubules of intact rat testes than is required to maintain quantitatively normal spermatogenesis and reveal for the first time that there is a dose-response relationship between the STF T concentration and the quantitative maintenance of advanced spermatogenic cells in the rat testis.

Effects of Bisphenol A on Testosterone Levels and Sexual Behaviors of Male Mice

“…As reported by previous articles, ITT is an absolute prerequisite for maintaining normal spermatogenesis [21] [22]. Normally, ITT concentration is roughly 50 -100 times higher than serum testosterone concentration [22]. So, we suppose that BPA might impair Leydig cells, decline ITT, and then suppress spermatogenesis.…”

“…The results displayed that BPA can decrease the testosterone concentration in serum and testicular tissue, and the effects were more obvious in higher dose group than in lower dose group. As reported by previous articles, ITT is an absolute prerequisite for maintaining normal spermatogenesis [21] [22]. Normally, ITT concentration is roughly 50 -100 times higher than serum testosterone concentration [22].…”

Effect of threonine on immunity and reproductive performance of male mice infected with pseudorabies virus

“…The process of spermatogenesis is regulated by a complex interplay of endocrine and paracrine signals. Intratesticular testosterone is believed to stimulate spermatogenesis directly in rats (Zirkin et al, 1989) and men (Matsumoto and Bremner, 1985). This notion was supported by the finding that higher dietary Thr increased testosterone concentration of male mice after being infected with PRV.…”

Paracrine regulation of cellular interactions in the testis: factors in search of a function

“…The androgen receptor binds its ligand in the cytoplasm, is translocated into the nucleus and stimulates the transcription of specific genes ( indicating that changes in the expression of the androgen receptor are not a major cause for defects of spermatogenesis (38). The testis contains at least fivefold more testosterone than needed for the maintenance of quantitative spermatogenesis and saturation of all receptor binding sites (40,41). The question which therefore arises for the local action of androgens is: how can a very abundant factor function as a local regulator?…”