Functional and molecular evidence for Na -HCO3 cotransporter in porcine vas deferens epithelia

Carlin, Ryan W., Rebecca R. Quesnell, Ling Zheng, Kathy E. Mitchell, and Bruce D. Schultz. Functional and molecular evidence for Na -HCO3 cotransporter in porcine vas deferens epithelia. Am J Physiol Cell Physiol 283: C1033–C1044, 2002. First published May 22, 2002; 10.1152/ ajpcell.00493.2001.—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 , HCO3 , and Cl for a full response. HCO3 dependent current was unaffected by acetazolamide, bumetanide, or amiloride but was inhibited by basolateral 4,4 diisothiocyanostilbene-2,2 -disulfonic acid. Na -driven, HCO3 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 HCO3 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.