Primary monolayer cultures of the epithelial cells from the rat cauda epididymidis had a basal transepithelial potential of 1.24 +/- 0.11 mV, apical side negative, a short-circuit current (SCC) of 2.42 +/- 0.17 microA/cm2, and a transepithelial resistance of 503 +/- 29.6 omega/cm2. Epinephrine (0.23 microM) added to the basolateral side caused a rise in the SCC (inward flowing) that was partially reversed by addition of amiloride, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), bumetanide, and acetazolamide to the basolateral side. In the absence of Cl or HCO3, the SCC response to epinephrine was reduced by 65 and 66%, respectively. Removal of K reduced the SCC response by 40%, whereas Na removal completely abolished it. A23187 and phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), stimulated the SCC when added to the apical side. Addition of the Cl channel blockers, anthracene-9-carboxylate and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) to the apical side reduced the SCC in a dose-dependent manner. It is concluded that anion secretion by the epididymis shares common mechanisms with other Cl-secreting epithelia.
IgG autoantibodies in human serum selectively bind to a glycopeptide antigen that appears on senescent and damaged cells in situ. We identified the membrane protein from which the senescent cell antigen is derived by using a phagocytosis-inhibition assay and immunoautoradiographic gel staining and electroblotting techniques. Results of the phagocytosis-inhibition assay revealed that only the purified transmembrane glycoprotein designated "band 3" and senescent cell antigen inhibited the phagocytosis of erythrocytes induced by IgG eluted from senescent erythrocytes. Purified spectrin, syndein, band 4.1, actin, glycophorin A, and intact or desialylated sialoglycoprotein periodic acid/Schiff (PAS) staining bands 1-4 containing glycophorins A, B, and C did not inhibit phagocytosis. Specific antibodies against the senescent cell antigen and erythrocyte band 3 were used to identify the membrane protein from which the senescent cell antigen is derived. Band 3-related polypeptides (Mrs 60,000,42,000, and 18-26,000) were identified in erythrocyte ghosts prepared in the presence of diisopropyl fluorophosphate, phenylmethylsulfonyl fluoride, and EDTA by immunoautoradiography with antiband 3. Antibodies to senescent cell antigen reacted with band 3 and the same lower Mr band 3-related polypeptides. Thus, the senescent cell antigen is immunologically related to band 3. oglycoprotein mixtures through it, a procedure that depleted
SUMMARY1. A microperfusion technique has been developed to study transport processes in the rat cauda epididymidis in vivo.2. Na+ and water were found to be reabsorbed by the perfused rat cauda epididymidis at the rates of 3-000 + 0-25 n-equiv cm-' min-(mean + s.E., n = 14) and 20-7 + 1-7 nl. cm-1 min-' (mean + s.E., n = 14) respectively. Reabsorption of Na+ was isotonic.3. K+ was found to be secreted into the ductal lumen at the rate of 0-124 + 0-016 n-equiv cm-1 min' (mean + S.E., n = 14).4. Na+ reabsorption and water reabsorption were abolished by removing Na+ ions from the perfusion medium. The dependence of rate of net Na+ reabsorption on the intraluminal Na+ ion concentration showed saturation kinetics, with the apparent K. values of about 20 mm Na+. The dependence of water reabsorption on the intraluminal Na+ ion concentration also followed closely that of Na+.5. Application of amiloride 10-4 M) to the perfusion fluid abolished both Na+ and water reabsorption by the rat cauda epididymidis.6. Removal of chloride from the perfusion fluid had no effect on Na+ and water reabsorption but increased the K+ secretion rate by threefold.7. Proteins were also found to be secreted by the rat cauda epididymidis at a rate of 11-7+ 1-8 ng cm-1 min-(mean+s.E., n = 11). The secretary rate was not dependent on the intraluminal Na+ ion concentration. 8. Castration in rats abolished the reabsorption of Na+ and water and secretion of K+ and proteins by the rat cauda epididymidis. These effects could be reversed by injecting testosterone propionate into castrated rats.9. The possible role of these transport processes in sperm maturation is discussed.
Secretion of electrolytes and water by the epididymal epithelium is important in the formation an optimal fluid environment for sperm maturation and transport. This process is disrupted in the genetic disease cystic fibrosis caused by mutation of the cystic fibrosis transmemebrane conductance regulator (CFTR) gene. Recent findings of CFTR gene mutations in healthy men with congenital bilateral absence of the vas deferens or poor sperm quality may indicate that CFTR gene mutations have a far-reaching effect on human reproduction.
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