Involvement of Na+-HCO3− Cotransporter in Mediating Cyclic Adenosine 3′,5′-Monophosphate-Dependent HCO3− Secretion by Mouse Endometrial Epithelium

Abstract The present study investigated the involvement of Na+-HCO3− cotransporter in mediating cAMP-stimulated HCO3− secretion across the cultured mouse endometrial epithelium using the short-circuit current (ISC) technique and intracellular pH measurement. Forskolin stimulated a rise in the ISC, 55.6% and 52.1% of which could be reduced by the removal of extracellular Cl− or by eliminating the contribution of Cl− secretion by bumetanide, an inhibitor of Na+-K+-2Cl− cotransporter, respectively. More than 80% reduction in the forskolin-induced ISC was obtained when both Cl− and HCO3− in the bath were removed or in HCO3−-free solution with bumetanide, indicating that the ISC depended on both Cl− and HCO3−. The presence of the Na+ channel-blocker amiloride in the apical solution did not reduce the forskolin-induced ISC; however, the ISC could be abolished by removing Na+ from the bathing solution, suggesting that the Cl−- and HCO3−-dependent ISC was also dependent on basolateral Na+. The forskolin-stimulate...