REGULATION OF THE TRANSPORT OF IMMUNOGLOBULIN-G INTO THE MALE-RAT REPRODUCTIVE-TRACT

The net movements of IgG in the rat testis and epididymis were studied using physiological techniques in conditions of anticipated subnormal organ concentrations of testosterone (T). The volume of extracellular fluid accessible to IgG per gram whole testis (V-eq, mu l/g) did not change but that per gram interstitial tissue decreased in intact rats treated with T to suppress gonadotrophin secretion. Estimates of surfa ce areas of the exchange vessels (S, cm(2)/g whole tissue) did not cha nge in any of the organs studied. The speed at which equilibrium betwe en tissue extracellular fluid and serum was reached(/K/, min(-1)), lym ph flow (Q(L), mu l/g/min) and estimates of microvascular permeability (P, nm/min) to IgG decreased in the testis of T-treated intact rats. In these animals, /K/ and P were higher than normal in the cauda. Afte r castration, /K/ and P decreased to near zero in the caput and corpus regions. The changes in /K/ and P due to castration could partly be p revented by T supplementation in the caput, but not in the corpus, whe re V-eq was supra-normal after T treatment. This difference in endothe lial response between caput and corpus indicates differences in contro l of endothelium and epithelium along the length of the epididymal duc t. In the testis of efferent duct-ligated (EDL) rats, P was lower than that in the intact rats, whereas in the corpus epididymidis of EDL ra ts, V-eq and P were higher than normal. The supra-normal V-eq values i n the corpus epididymidis of EDL and castrated T-treated rats suggest that the epithelial barrier leaks in the corpus when luminal testoster one is low. It is concluded that during testosterone administration to normal rats, the testicular and epididymal epithelial barrier remains intact, that trans-endothelial transport of IgG and extracellular flu id volume decrease in the testicular interstitium and that in conditio ns of low serum T, the endothelium of microvessels in the caput and co rpus epididymidis forms a barrier to IgG.