17 beta-estradiol effects on mast cell number and spermatogonial mitotic index in the testis of the frog, Rana esculenta.

Estrogen affects mast cell activity and cellular proliferation in several vertebrate tissues. Due to the presence of mast cells in the interstitial tissue of the testis and due to the annual changes of spermatogonial proliferation and estradiol level in the frog, Rana esculenta, we have studied the possible regulation of mast cell number (MCN) and primary spermatogonial mitosis exerted by 17 beta-estradiol (E2). MCN changed in the testis during the annual reproductive cycle, showing peaks in December and in May. Administration of E2 elicited an increase of MCN both in intact and hypophysectomized frogs, and this effect was counteracted by tamoxifen. In vitro experiments indicated that E2 induced an increase of both MCN and the primary spermatogonial mitotic index. Moreover, a significant decrease of intratesticular androgen content was measured in E2-treated testes. All the in vitro effects induced by E2 were counteracted by tamoxifen. In conclusion, our data indicate that in Rana esculenta testis E2 increase MCN and primary spermatogonial mitotic index via intratesticular mechanisms. A possible involvement of the decrease of androgen levels exerted by E2 in the mechanism underlying the increase of MCN is also considered.