The effect of external potassium (K) and cesium (Cs) on the inwardly rectifying K channel ROMK2 (K(ir)1.1b) was studied in Xenopus oocytes. Elevating external K from 1 to 10 mM increased whole-cell outward conductance by a factor of 3.4 +/- 0.4 in 15 min and by a factor of 5.7 +/- 0.9 in 30 min (n = 22). Replacing external Na by Cs blocked inward conductance but increased whole-cell conductance...

ROMK channels are regulated by internal pH (pH i ) and extracellular K (K o ). The mechanisms underlying this regulation were studied in these channels after expression in Xenopus oocytes. Replacement of the COOH-terminal portion of ROMK2 (Kir1.1b) with the corresponding region of the pH-insensitive channel IRK1 (Kir 2.1) produced a chimeric channel (termed C13) with enhanced sensitivity to inh...

We previously demonstrated that dietary K intake regulates the expression of Src family PTK, which plays an important role in controlling the expression of ROMK1 in plasma membrane (Wei Y, Bloom P, Lin D-H, Gu RM, and Wang WH. Am J Physiol Renal Physiol 281: F206-F212, 2001). In the present study, we used the immunofluorescence staining technique to demonstrate the presence of c-Src, a member o...

The cystic fibrosis transmembrane regulator (CFTR) is a Cl - channel. Mutations of this transporter lead to a defect of chloride secretion by epithelial cells causing the Cystic Fibrosis disease (CF). In spite of the high expression of CFTR in the kidney, patients with CF do not show major renal dysfunction, but it is known that both the urinary excretion of drugs and the renal capacity to conc...

The ability of intracellular and extracellular Mg(2+) to block secretory K(+) currents through ROMK channels under physiologic conditions is incompletely understood. We expressed ROMK2 channels in Xenopus oocytes and measured unitary currents in the inside-out and cell-attached modes of the patch-clamp technique. With 110 mM K(+) on both sides of the membrane, 0.2 to 5 mM Mg(2+) on the cytoplas...