Factors affecting the entry of testosterone into the lumen of the cauda epididymidis of the anaesthetized rat

Abstract

When [3H]testosterone was infused into the general circulation of the rat, perfusion of a length of the cauda epididymidis (17 .+-. 1.0 (mean .+-. SE) cm, n = 36) with perfusates of varied composition revealed a low entry of radioactivity (1-10% plasma levels; 10 exps [experiments]) with protein-free perfusates, and a greater entry (15-48%; 10 exps) when the perfusate contained bovine serum albumin (BSA 38 mg/ml). When the perfusate contained ovine or rat testicular fluid, or rat epididymal fluid at protein concentrations of 3 mg/l or less, the entry of radioactivity into the epididymis was greater than when the perfusate contained 3 mg BSA/ml. The addition of ovine rete testis fluid protein (3 mg/ml) to BSA (38 mg/ml) in the perfusate increased the uptake of radioactivity (58-106%; 6 exps). Radioactivity in blood was principally associated with testosterone (90, 95% total blood activity, 2 rats), whereas both [3H]testosterone (37, 41% total perfusate activity) and [3H]dihydrotestosterone (42, 63% total perfusate activity) were present in BSA-containing perfusates. The proportion of dihydrotestosterone appeared to increase when the perfusate contained protein of testicular origin.