Effect of temperature and pregnant mare's serum gonadotropin on testicular function in the spiny-tailed lizard, Uromastix hardwicki

Abstract

The effect of temperature and pregnant mare's serum gonadotropin (PMSG) was observed on the testes of Uromastix hardwicki at a time of the year (November) when the seminiferous epithelium contained abundant proliferating spermatogonia and some primary spermatocytes. This recrudescent state of the testes was maintained by keeping the animals at 20° for 10 days. But, in lizards kept at 35°, there was a marked decrease in the testis weight. The seminiferous tubules were lined mostly with Sertoli cells and a few resting types of spermatogonia. The interstitial cells were only slightly affected and there was no reduction in androgen concentrations in the testicular tissue or plasma, as measured by testosterone radioimmunoassay. At 20°, injections of 20 IU of PMSG daily for 10 days induced an increase in the number of primary spermatocytes and production of spermatids in certain regions of the tubules. In the PMSG-treated lizards kept at 35° the testes contained a single layer of resting spermatogonia placed along the basement membrane. Under these conditions PMSG failed to maintain the active state of the seminiferous epithelium. Unlike the germinal cells, the interstitial cells were markedly stimulated by PMSG at 20 or 35°. Testicular and plasma androgen levels were increased severalfold in gonadotropin-treated lizards. The elevation of androgen levels as a result of PMSG stimulation was higher in lizards kept at 35°. It is suggested that in Uromastix hardwicki, the germinal epithelium responds differentially to PMSG treatment at the two different temperatures and that the activity of the interstitial cells is not inhibited by hyperthermia.