Transepithelial movement of non-polar and polar compounds in male rat reproductive tubule examined by in vivo microperifusion and in vivo micropuncture

Proluminal movement of 3H-testosterone and 3H-sucrose from peritubular to intratubular fluids of the adult rat testis and epididymis was investigated by using in vivo microperifusion and subsequent micropuncture of seminiferous tubules and caput, corpus, and cauda epididymal tubules. Tubules were perifused with Minimum Essential Medium containing 3H-testosterone or 3H-sucrose. 14C-polyethyleneglycol was included in the perifusion fluid as a marker for contamination of intraluminal fluid by interstitial fluid. Radioactivity of isotopes in perifusion and intraluminal fluids was determined at one and two hours after perifusion and the percentage of peritubular isotopes appearing in intraluminal fluid was determined. Net entry of 3H-sucrose into the seminiferous and epididymal tubules was significantly reduced. Proluminal movement of 3H-androgen across the seminiferous epithelium was also restricted. In contrast, intraluminal 3H-androgen concentrations in caput epididymal fluid were 200 to 300% of those in peritubular fluid at both one and two hours after perifusion. Similar results were found in the corpus epididymidis. 3H-androgen concentrations in cauda epididymal fluid were approximately 125% of peritubular isotope concentrations. The exact mechanism underlying this uphill proluminal movement of 3H-androgen into the rat epididymal lumen remains to be elucidated.