Dietary K+ regulates apical membrane expression of maxi-K channels in rabbit cortical collecting duct

The cortical collecting duct (CCD) is a final site for regulation of K+ homeostasis. CCD K+ secretion is determined by the electrochemical gradient and apical permeability to K+. Conducting secretory K+ (SK/ROMK) and maxi-K channels are present in the apical membrane of the CCD, the former in principal cells and the latter in both principal and intercalated cells. Whereas SK channels mediate baseline K+ secretion, maxi-K channels appear to participate in flow-stimulated K+ secretion. Chronic dietary K+ loading enhances the CCD K+ secretory capacity due, in part, to an increase in SK channel density (Palmer et al., J Gen Physiol 104: 693–710, 1994). Long-term exposure of Ambystoma tigrinum to elevated K+ increases renal K+ excretion due to an increase in apical maxi-K channel density in their CDs (Stoner and Viggiano, J Membr Biol 162: 107–116, 1998). The purpose of the present study was to test whether K+ adaptation in the mammalian CCD is associated with upregulation of maxi-K channel expression. New Zea...