AJP - Renal Physiology, Vol 270, Issue 1 69-F81, Copyright © 1996 by American Physiological Society

ARTICLES

Coexistence of two types of Ca(2+)-activated K+ channels in rat renal arterioles

D. Gebremedhin, M. Kaldunski, E. R. Jacobs, D. R. Harder and R. J. Roman
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226, USA.

Single-channel K+ currents were characterized in vascular smooth muscle cells freshly isolated from preglomerular arterioles (15-40 microns OD) of the rat. Under conditions of symmetrical K+ (145 mM), two types of single-channel K+ currents with unitary slope conductances of 68 +/- 2.6 and 251 +/- 4.9 pS were recorded from excised inside-out membrane patches. The open state probability (NPo) of these two types of K+ channels was voltage sensitive and the channels were highly selective for K+ over Na+. Elevation of intracellular calcium concentration ([Ca2+]i) from 0.1 to 0.5 microM on the cytoplasmic face of inside-out patches increased the frequency of opening and the NPo of both the 68-pS and the 251-pS K+ channels. Application of ATP (0.1-1 mM) to the internal surface of inside-out patches had no effect on the activities of both channel types. Internally applied Ba2+ (1 mM) blocked both of these channels. Externally applied tetraethylammonium (0.1-0.3 mM) or charybdotoxin (50 nM) blocked both the 68-pS and the 251-pS K+ channels. Externally applied apamin (50 nM), however, selectively blocked the 68-pS K+ channel but had no effect on the frequency of opening of the 251-pS K+ channel. Apamin also reduced macroscopic K+ current recorded from voltage-clamped rat renal arteriolar muscle cells by 25-30%. These results indicate the coexistence of two types of Ca(2+)-activated K+ channels in the membranes of vascular smooth muscle cell isolated from renal preglomerular arterioles of the rat that differ in unitary conductances and pharmacological properties.

This article has been cited by other articles:

				C. M. Troncoso Brindeiro, R. W. Fallet, P. H. Lane, and P. K. Carmines Potassium channel contributions to afferent arteriolar tone in normal and diabetic rat kidney Am J Physiol Renal Physiol, July 1, 2008; 295(1): F171 - F178. [Abstract] [Full Text] [PDF]

				D. Gebremedhin, K. Yamaura, and D. R. Harder Role of 20-HETE in the hypoxia-induced activation of Ca2+-activated K+ channel currents in rat cerebral arterial muscle cells Am J Physiol Heart Circ Physiol, January 1, 2008; 294(1): H107 - H120. [Abstract] [Full Text] [PDF]

				L. Balasubramanian, A. Ahmed, C.-M. Lo, J. S. K. Sham, and K.-P. Yip Integrin-mediated mechanotransduction in renal vascular smooth muscle cells: activation of calcium sparks Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2007; 293(4): R1586 - R1594. [Abstract] [Full Text] [PDF]

				L. Magnusson, C. M. Sorensen, T. H. Braunstein, N.-H. Holstein-Rathlou, and M. Salomonsson Renovascular BKCa channels are not activated in vivo under resting conditions and during agonist stimulation Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R345 - R353. [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]

				J. L. Pluznick, P. Wei, P. K. Carmines, and S. C. Sansom Renal fluid and electrolyte handling in BKCa-beta 1-/- mice Am J Physiol Renal Physiol, June 1, 2003; 284(6): F1274 - F1279. [Abstract] [Full Text] [PDF]

				D. Gebremedhin, K. Yamaura, C. Zhang, J. Bylund, R. C. Koehler, and D. R. Harder Metabotropic Glutamate Receptor Activation Enhances the Activities of Two Types of Ca2+-Activated K+ Channels in Rat Hippocampal Astrocytes J. Neurosci., March 1, 2003; 23(5): 1678 - 1687. [Abstract] [Full Text] [PDF]

				R. W. Fallet, J. P. Bast, K. Fujiwara, N. Ishii, S. C. Sansom, and P. K. Carmines Influence of Ca2+-activated K+ channels on rat renal arteriolar responses to depolarizing agonists Am J Physiol Renal Physiol, April 1, 2001; 280(4): F583 - F591. [Abstract] [Full Text] [PDF]

				W.-L. Chan, N.-H. Holstein-Rathlou, and K.-P. Yip Integrin mobilizes intracellular Ca2+ in renal vascular smooth muscle cells Am J Physiol Cell Physiol, March 1, 2001; 280(3): C593 - C603. [Abstract] [Full Text] [PDF]

				C.-W. Sun, J. R. Falck, H. Okamoto, D. R. Harder, and R. J. Roman Role of cGMP versus 20-HETE in the vasodilator response to nitric oxide in rat cerebral arteries Am J Physiol Heart Circ Physiol, July 1, 2000; 279(1): H339 - H350. [Abstract] [Full Text] [PDF]

				R. A. Kramp, P. Fourmanoir, L. Ladriere, E. Joly, C. Gerbaux, A. el Hajjam, and N. Caron Effects of Ca2+ channel activity on renal hemodynamics during acute attenuation of NO synthesis in the rat Am J Physiol Renal Physiol, April 1, 2000; 278(4): F561 - F569. [Abstract] [Full Text] [PDF]

				J. M. Doughty, F. Plane, and P. D. Langton Charybdotoxin and apamin block EDHF in rat mesenteric artery if selectively applied to the endothelium Am J Physiol Heart Circ Physiol, March 1, 1999; 276(3): H1107 - H1112. [Abstract] [Full Text] [PDF]

				C.-W. Sun, M. Alonso-Galicia, M. R. Taheri, J. R. Falck, D. R. Harder, and R. J. Roman Nitric Oxide-20–Hydroxyeicosatetraenoic Acid Interaction in the Regulation of K+ Channel Activity and Vascular Tone in Renal Arterioles Circ. Res., November 30, 1998; 83(11): 1069 - 1079. [Abstract] [Full Text] [PDF]

				D. Zhu, R. M. Effros, D. R. Harder, R. J. Roman, and E. R. Jacobs Tissue Sources of Cytochrome P450 4A and 20-HETE Synthesis in Rabbit Lungs Am. J. Respir. Cell Mol. Biol., July 1, 1998; 19(1): 121 - 128. [Abstract] [Full Text]

				O. Ito, M. Alonso-Galicia, K. A. Hopp, and R. J. Roman Localization of cytochrome P-450 4A isoforms along the rat nephron Am J Physiol Renal Physiol, February 1, 1998; 274(2): F395 - F404. [Abstract] [Full Text] [PDF]