AJP - Renal Physiology, Vol 267, Issue 3 489-F496, Copyright © 1994 by American Physiological Society

ARTICLES

ATP-sensitive K(+)-selective channels of inner medullary collecting duct cells

S. C. Sansom, T. Mougouris, S. Ono and T. D. DuBose Jr
Department of Medicine, University of Texas, Houston 77030.

The inner medullary collecting duct (IMCD) in vivo has the capacity to either secrete or reabsorb K+. However, a selective K+ conductance has not been described previously in the IMCD. In the present study, the patch-clamp method was used to determine the presence and properties of K(+)-selective channels in the apical membrane of the inner medullary collecting duct cell line, mIMCD-3. Two types of K(+)-selective channels were observed in both cell-attached and excised patches. The most predominant K+ channel, a smaller conductance K+ channel (SK), was present in cell-attached patches with 140 mM KCl (high bath K+) but not with 135 mM NaCl plus 5 mM KCl (low bath K+) in the bathing solution. The single-channel conductance of SK was 36 pS with inward currents and 29 pS with outward currents in symmetrical 140 mM KCl. SK was insensitive to both voltage and Ca2+. However, SK was inhibited significantly by millimolar concentrations of ATP in excised patches. A second K(+)-selective channel [a larger K+ channel (BK)] displayed a single-channel conductance equal to 132 pS with inward currents and 90 pS with outward currents in symmetrical 140 mM KCl solutions. BK was intermittently activated in excised inside-out patches by Mg(2+)-ATP in concentrations from 1 to 5 mM. With complete removal of Mg2+, BK was insensitive to ATP. BK was also insensitive to potential and Ca2+ and was observed in cell-attached patches with 140 mM KCl in the bath solution. Both channels were blocked reversibly by 1 mM Ba2+ from the intracellular surface but not by external Ba2+.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				M. E. Handlogten, S.-P. Hong, C. M. Westhoff, and I. D. Weiner Apical ammonia transport by the mouse inner medullary collecting duct cell (mIMCD-3) Am J Physiol Renal Physiol, August 1, 2005; 289(2): F347 - F358. [Abstract] [Full Text] [PDF]

				S. C. Hebert, G. Desir, G. Giebisch, and W. Wang Molecular Diversity and Regulation of Renal Potassium Channels Physiol Rev, January 1, 2005; 85(1): 319 - 371. [Abstract] [Full Text] [PDF]

				M. E. Handlogten, S.-P. Hong, C. M. Westhoff, and I. D. Weiner Basolateral ammonium transport by the mouse inner medullary collecting duct cell (mIMCD-3) Am J Physiol Renal Physiol, October 1, 2004; 287(4): F628 - F638. [Abstract] [Full Text] [PDF]

				S.-L. Xia, L. Wang, M. N. Cash, X. Teng, R. A. Schwalbe, and C. S. Wingo Extracellular ATP-induced calcium signaling in mIMCD-3 cells requires both P2X and P2Y purinoceptors Am J Physiol Renal Physiol, August 1, 2004; 287(2): F204 - F214. [Abstract] [Full Text] [PDF]

				L. I. Escobar, J. C. Martinez-Tellez, M. Salas, S. A. Castilla, R. Carrisoza, D. Tapia, M. Vazquez, J. Bargas, and J. J. Bolivar A voltage-gated K+ current in renal inner medullary collecting duct cells Am J Physiol Cell Physiol, April 1, 2004; 286(4): C965 - C974. [Abstract] [Full Text] [PDF]

				D. P. Wallace, L. A. Rome, L. P. Sullivan, and J. J. Grantham cAMP-dependent fluid secretion in rat inner medullary collecting ducts Am J Physiol Renal Physiol, June 1, 2001; 280(6): F1019 - F1029. [Abstract] [Full Text] [PDF]

				J.-F. Noulin, E. Brochiero, J.-Y. Lapointe, and R. Laprade Two types of K+ channels at the basolateral membrane of proximal tubule: inhibitory effect of taurine Am J Physiol Renal Physiol, August 1, 1999; 277(2): F290 - F297. [Abstract] [Full Text] [PDF]

				S. M. Wall Ouabain reduces net acid secretion and increases pHi by inhibiting NH+4 uptake on rat tIMCD Na+-K+-ATPase Am J Physiol Renal Physiol, December 1, 1997; 273(6): F857 - F868. [Abstract] [Full Text] [PDF]