PITUITARY GONADOTROPINS REGULATE SPERMATOGONIAL DIFFERENTIATION AND PROLIFERATION IN THE RAT

The relative regulatory roles of the pituitary gonadotropins, luteiniz ing hormone and follicle stimulating hormone in the spermatogonial pro liferation has been studied using specific antibodies against these ho rmones in the immature rats. Immunoneutralization of luteinizing hormo ne for 7 days resulted in significant reduction in tetraploid cells an d total absence of haploid cells, while there was a relative increase in the diploid population. This was also accomopanied by a decrease in spermatogonial proliferation as indicated by a decrease in [H-3] thym idine incorporation into DNA by purified spermatogonia. Administration bf follicle stimulating hormone als for 7 days also caused a signific ant decrease in the rate of spermatogonial proliferation. Withdrawal o f follicle stimulating hormone led to a significant reduction in tetra ploid and haploid cells However interestingly, it failed to totally ab olish the appearance of these cells. Administration of testosterone (3 mg/day/rat) for 2 days along with the gonadotropin a/s could partially reverse the effect on spermatogonial proliferation. It is concluded t hat (i) both luteinizing hormone and follicle stimulating hormone are involved in spermatogonial proliferation, (ii) lack of testosterone co nsequent of the neutralization of luteinizing hormone prevented the en try of spermatogonial cells into meiosis, (iii) testosterone may be in volved in spermatogonial proliferation providing a mitotic signal and (v) both follicle stimulating hormone and testosterone act synergistic ally and lack of any one of the hormones results in impairment of sper matogonial proliferation.