Abstract
Ion channels present in the apical membrane of cultured mouse renal collecting tubule (M-1) principal cells were investigated using the patch-clamp technique. Two types of channel current, small current with high open probability (Po) and intermediate current with low Po, were observed in the apical surface of confluent mono-layered M-1 principal cells in cell-attached patches under the control condition. It was revealed that the small current was formed by inwardly rectifying small conductance (20–30 pS) K+ (SK) channels, and the intermediate current was formed by non-selective cation (NSC) channels with the conductance of about 40 pS. Addition of 8-BrcAMP (100 μM) to the bath solution enhanced activity of the SK channel, whereas that of KT5720 (500 nM), an inhibitor of protein kinase A (PKA), suppressed it in cell-attached patches. However, neither 8-BrcAMP nor KT5720 induced appreciable change in activity of the NSC channel. In inside-out patches, the SK channel required 1 mM MgATP in the cytoplasmic surface to maintain its activity, while the NSC channel was activated by cytoplasmic Ca2+. From these basic properties, it is suggested that the SK channel is an ATP-regulated channel which is subject to ROMK channel family, although the molecular identification of the SK channel as well as that of the NSC channel remains to be investigated. Further studies will be necessary to clarify the physiological roles of these ion channels in the function of mouse kidney collecting tubule. [J Physiol Sci. 2007;57 Suppl:S120]
