Interstitial fluid volume in the rat testis: androgen-dependent regulation by the seminiferous tubules?

Regulation of testicular interstitial fluid (IF) volume has been investigated in adult male rats in which the Leydig cells were selectively destroyed with a single i.p. injection of ethane dimethane sulphonate (EDS). Following this treatment, some animals also received testosterone supplementation by s.c. injection every 3 days, beginning either from the time of EDS injection, or 3-12 days afterwards. The volume of IF obtained by drip collection was determined, and testosterone and gonadotrophin concentrations measured in blood and in IF. Testosterone levels in IF and serum became undetectable by 3 days after EDS treatment. IF volume was reduced by 50% (P less than 0.01) to reach a minimum level between 6 and 9 days after treatment. However, this decline was prevented in the absence of Leydig cells by supplementation with testosterone from the time of EDS injection, a treatment which also kept gonadotrophins at minimum or undetectable levels. Furthermore, the reduced IF volume seen up to 9 days after treatment with EDS alone could be restored to control levels within 3 days by a single injection of testosterone. The results obtained demonstrate that androgens, but not Leydig cells or gonadotrophins, are required for the maintenance of interstitial fluid volume in the adult rat testis. It is suggested that the seminiferous tubules may mediate this response, through an androgen-dependent mechanism.