Functional and molecular evidence for Na+-HCO 3 − cotransporter in porcine vas deferens epithelia

Abstract

This study focused on the role of sodium-bicarbonate cotransporter (NBC1) in cAMP-stimulated ion transport in porcine vas deferens epithelium. Ion substitution experiments in modified Ussing chambers revealed that cAMP-mediated stimulation was dependent on the presence of Na+, HCO[Formula: see text], and Cl− for a full response. HCO[Formula: see text]-dependent current was unaffected by acetazolamide, bumetanide, or amiloride but was inhibited by basolateral 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. Na+-driven, HCO[Formula: see text]-dependent, stilbene-inhibitable anion flux was observed across the basolateral membrane of selectively permeabilized monolayers. Results of radiotracer flux studies suggest a 4,4′-dinitrostilbene-2,2′-disulfonate-sensitive stoichiometry of 2 base equivalents per Na+. Antibodies raised against rat kidney NBC epitopes (rkNBC; amino acids 338–391 and 928–1035) identified a single band of ∼145 kDa. RT-PCR detected NBC1 message in porcine vas deferens epithelia. These results demonstrate that vas deferens epithelial cells possess the proteins necessary for the vectoral transport of HCO[Formula: see text] and that these mechanisms are maintained in primary culture. Taken together, the results indicate that vas deferens epithelia play an active role in male fertility and have implications for our understanding of the relationship between cystic fibrosis and congenital bilateral absence of the vas deferens.