Evidence for electrogenic Na-glucose cotransport in tracheal epithelium.

We demonstrate that electrogenic glucose coupled Na+ absorption accounts for about 20% of the residual, amiloride and Cl- insensitive, Na+ transport in isolated (equine) trachea. Either glucose removal from the mucosal side or addition of 10(-4) M phloridzin, a known pharmacological inhibitor of Na-glucose cotransport in small intestine and kidney proximal tubule, results in depolarization (lumen referenced to bath) of the transepithelial potential difference (Vt) and in a significant decrease of the equivalent short circuit current Ieq by 4 mV and 4 microA/cm2, respectively, without affecting the transepithelial resistance (Rt). Neither glucose removal nor the application of phloridzin on the basolateral side have a significant or consistent effect on the bioelectric parameters.