Age-related changes in responsiveness of rat Leydig cells to hCG

Abstract

The responsiveness of decapsulated testes and isolated Leydig cell preparations from rats (30-80 days of age) to a constant dose of 3 ng hCG[human chorionic gonadotropin]/2 ml was assessed by comparison of the production of testosterone and total 17.beta.-hydroxy androgen (17.beta.-HA). When testosterone secretion was used as the index of response, there was a marked increase in the production with age by decapsulated testes and also by equal numbers of Leydig cells. When 17.beta.-HA was taken as the response parameter this increase was only marginal for the decapsulated testes and there was an age-dependent decrease when expressed per 106 cells. These differences probably reflect changes in the metabolism of testosterone to 5.alpha.-reduced products with increasing age because 80% of androgen secreted at 30 days is 3.alpha.-androstanediol and 86% is secreted as testosterone at 80 days. For studies on hCG responsiveness and the steroidogenic capacity of immature rat Leydig cells, testosterone is an inappropriate response parameter and this response undergoes a decrease rather than an increase during prepubertal development.