Spermatogenic Defects in a New Inbred Strain SD/gShi Male Rat with Small Testes.

Abstract

A new inbred strain SD/gShi male rat with small testes was studied from the reproductive, histopathological and endocrinological viewpoints from 3 to 35 weeks of age. SD/gShi males showed only a slight increase in sperm production at puberty, in contrast to a rapid increase in normal SD males. At 6 weeks of age, spermiation became detectable in both SD/gShi and normal SD males, however, the numbers of spermatocytes and round spermatids per Sertoli cell in SD/gShi males were less than those in normal SD males. Moreover, the number of round spermatids per Sertoli cell did not increase in SD/gShi males at puberty, while they did in normal SD males. Histological analysis of germ cell numbers in SD/gShi males indicated that the lower numbers of spermatocytes and spermatids are caused by suppression of germ cell proliferation at the step from the spermatogonium to the preleptotene spermatocyte. Adult SD/gShi males showed normal fertilization ability, however, they had only 10-20% of sperm production in normal adult SD males and showed depressed sperm motion. Plasma total testosterone in SD/gShi males was lower for all ages, though testis testosterone concentration was normal. Plasma gonadotropin concentrations, especially FSH, remained higher than in normal SD males, suggesting that the spermatogenic defects are not caused by gonadotropin deficiency. These results indicate that the SD/gShi male is characterized by spermatogenic defects at the preleptotene spermatocyte step which occur from the first spermatogenic wave. The SD/gShi male rat can serve as a useful model for studying spermatogenesis in rats.