Relationship between testosterone, fluid content and luteinizing hormone receptors in the rat testis.

Injection of immature male rats with human chorionic gonadotrophin resulted in a decreased ability of the testis to bind [¹²⁵I]-labelled human chorionic gonadotrophin $\text{in vitro}$, and a marked, but transient increase in testis weight; the latter was apparently due to the accumulation of fluid containing high levels of testosterone. Intra-testicular injection of cycloheximide significantly inhibited all these changes, thus demonstrating their dependence on protein synthesis. It is concluded from this and other data that either testosterone itself or a steroidogenic protein intermediary may be responsible for the gonadotrophin-induced reduction in availability of gonadotrophin receptors.