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 seve ral vertebrate tissues. Due to the presence of mast cells in the inter stitial tissue of the testis and due to the annual changes of spermato gonial 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 (E-2) MCN changed in the testis during the annual reproductive cycle, showing pe aks in December and in May. Administration of E-2 elicited an increase of MCN both in intact and hypophysectomized frogs, and this effect wa s counteracted by tamoxifen. In vitro experiments indicated that E-2 i nduced an increase of both MCN and the primary spermatogonial mitotic index. Moreover, a significant decrease of intratesticular androgen co ntent was measured in E-2-treated testes. All the in vitro effects ind uced by E-2 were counteracted by tamoxifen. in conclusion, our data in dicate that in Rana esculenta testis E-2 increases MCN and primary spe rmatogonial mitotic index via intratesticular mechanisms. A possible i nvolvement of the decrease of androgen levels exerted by E-2 in the me chanism underlying the increase of MCN is also considered. (C) 1997 Wi ley-Liss, Inc.