抄録
The ductal system of the exocrine pancreas produces a HCO3−-rich fluid secretion in response to secretin and some other simuli. Basolateral K+ channels provide an exit pathway for K+ brought in by the basolateral Na+-K+-ATPase and play a vital role in maintaining the membrane potential, which is a crucial component of the driving force for anion secretion. Using electrophysiological and molecular techniques, we investigated molecular nature of K+ channels which contribute to the resting membrane potential in pancreatic duct cells. In whole-cell recordings from freshly isolated interlobular duct cells, we observed a strongly inwardly rectifying K+ (Kir) current, which displayed an approximate square-root dependence of conductance on extracellular K+ concentration and a high degree of selectivity for K+. The currents were blocked by extracellular Ba2+ in a voltage-dependent manner. Cell-attached single-channel recording identified 40 pS K+ channels that are most likely to mediate whole-cell Kir currents. RT-PCR of RNA from rat pancreas revealed transcripts of rat Kir2.1, Kir2.2, and Kir2.4. Immunohistochemical studies showed Kir2.1, Kir2.2 and Kir2.4 immunoreactivity in pancreatic duct cells. These results suggest that Kir2 subunits may mediate native Kir currents responsible for setting the resting membrane potential and might be, at least in part, involved in HCO3− secretion in pancreatic duct cells. [J Physiol Sci. 2008;58 Suppl:S210]
