Depletion of the Cytoplasmic Estrogen Receptor in Gonadotropin-Desensitized Testes*

Abstract

Recent studies have shown that hCG stimulates 17β-estradiol production in the testis, and a possible role for 17β- estradiol in hCG-induced desensitization of testosterone synthesis has been suggested. These studies were initiated to examine the testicular content of cytoplasmic estrogen receptor in relation to hCG-induced desensitization of testosterone production 24 h and 5 days after a sc injection of hCG. Twenty-four hours after the injection of 30, 300, and 3000IU hCG, pronounced (82- 88%) depletion of the cytoplasmic estrogen receptor was observed, while a 3-IU dose elicited a 41% depletion. A concomitant desensitization to hCG stimulation in vitro was observed after the injection of 30, 300, and 3000 IU hCG, as reflected by a lack of stimulation of testosterone production above that in matched controls. Testicular 17β-estradiol levels rose significantly after the injection of 300 or 3000 IU hCG. Five days after the injection of hCG, full replenishment of the cytoplasmic estroge n receptor had occurred in the 3- and 30-IU dose groups, while partial replenishment (22-56% depletion) had occurred with the 300- and 3000-IU dose groups. Only the 3000-IU dose group remained desensitized to hCG stimulation in vitro at this time point. Results indicated that occupancy by endogenous 17β-estradiol was not a factor, thus suggesting a true receptor depletion phenomenon. These results demonstrate that hCG-induced desensitization of testicular steroidogenesis is accompanied by depletion of the cytoplasmic estrogen receptor. Further, replenishment of the estrogen receptor at 5 days was accompanied by a return of the testicular response to hCG.