ROMK channels play a key role in overall K balance by controlling K secretion across the apical membrane of mammalian cortical collecting tubule. In contrast to the family of strong inward rectifiers (IRKs), ROMK channels are markedly sensitive to intracellular pH. Using Xenopus oocytes, we have confirmed this pH sensitivity at both the single-channel and whole cell level. Reduction of oocyte p...

We have previously demonstrated that the ROMK channel maintains the property of arachidonic acid (AA) sensitivity observed originally in the native ATP-sensitive K+channel of the rat cortical collecting duct (16). We used the patch-clamp technique to extend these studies to other NH2-terminal splice variants of the ROMK channel family, ROMK2 and ROMK3, expressed in Xenopus oocytes to determine ...

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 ...

Previous studies suggested that the cytoplasmic COOH-terminal portions of inward rectifier K channels could contribute significant resistance barriers to ion flow. To explore this question further, we exchanged portions of the COOH termini of ROMK2 (Kir1.1b) and IRK1 (Kir2.1) and measured the resulting single-channel conductances. Replacing the entire COOH terminus of ROMK2 with that of IRK1 de...

Macica, Carolyn M., Yinhai Yang, Kenneth Lerea, Steven C. Hebert, and WenHui Wang. Role of the NH2 terminus of the cloned renal K1 channel, ROMK1, in arachidonic acid-mediated inhibition. Am. J. Physiol. 274 (Renal Physiol. 43): F175–F181, 1997.—We have previously demonstrated that the ROMK channel maintains the property of arachidonic acid (AA) sensitivity observed originally in the native ATP...

Permeation, gating, and their interrelationship in an inwardly rectifying potassium (K+) channel, ROMK2, were studied using heterologous expression in Xenopus oocytes. Patch-clamp recordings of single channels were obtained in the cell-attached mode. The gating kinetics of ROMK2 were well described by a model having one open and two closed states. One closed state was short lived (approximately...

The renal outer medulla K+ channel (ROMK) family of K+ channels may constitute a major pathway for K+ secretion in the distal nephron. To date, four main isoforms of this gene have been identified in the rat that differ only in their NH2-terminal amino acids and that share a common "core exon" that determines the remaining protein sequence. Using RT-PCR, we have identified a new set of ROMK iso...

Beesley, A. H., B. Ortega, and S. J. White. Splicing of a retained intron within ROMK K1 channel RNA generates a novel set of isoforms in rat kidney. Am. J. Physiol. 276 (Cell Physiol. 45): C585–C592, 1999.—The renal outer medulla K1 channel (ROMK) family of K1 channels may constitute a major pathway for K1 secretion in the distal nephron. To date, four main isoforms of this gene have been iden...

Close similarity between the rat native low-conductance K(+) channel in the apical membrane of renal cortical collecting duct principal cells and the cloned rat ROMK channel strongly suggest that the two are identical. Prominent features of ROMK regulation are a steep pH dependence and activation by protein kinase A (PKA)-dependent phosphorylation. In this study, we investigated the pH dependen...