Evidence for a role of the Leydig cells in control of the intratesticular secretion of inhibin.

Injection of adult male rats with human chorionic gonadotrophin (hCG) caused a dose- and time-dependent increase in the levels of immunoactive inhibin in testicular interstitial fluid (IF), which differed from the pattern of change in testosterone levels. Blockage of the hCG-induced increase in IF levels of testosterone, by administration of aminoglutethimide, only partially attenuated the increase in levels of inhibin. Inhibin levels in IF were only increased by doses of hCG which cause inflammatory changes and focal seminiferous tubule damage, but there was no association between the degree of tubule damage and inhibin levels. It is concluded that one or more luteinizing hormone (LH)-regulated, non-steroidogenic Leydig cell products may be involved in the paracrine control of inhibin secretion. These data are of clinical relevance and of potential physiological significance.