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| REGULATION OF THE HYPERPOLARIZATION-ACTIVATED K+ CHANNEL IN THE LATERAL MEMBRANE OF THE CORTICAL COLLECTING DUCT |
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| Author(s): WANG WH |
| Source: JOURNAL OF GENERAL PHYSIOLOGY Volume: 106 Issue: 1 Pages: 25-43 Published: JUL 1995 |
| Times Cited: 28 References: 33 |
| Abstract: An intermediate-conductance K+ channel (I.K.), the activity of which is increased by hyperpolarization, was previously identified in the lateral membrane of the cortical collecting duct (CCD) of the rat kidney (Wang, W. H., C. M. McNicholas, A. S. Segal, and G. Giebisch. 1994. American Journal of Physiology. 266:F813-F822). The biophysical properties and regulatory mechanisms of this K+ channel have been further investigated with patch clamp techniques in the present study. The slope conductance of the channel in inside-out patches was 50 pS with 140 mM KCl in the pipette and 5 mM KCl, 140 mM NaCl (NaCl Ringer's solution) in the bath. Replacement of the bath solution with symmetrical 140 mM KCI solution changed the slope conductance of the channel to 85 pS and shifted the reversal potential by 55 mV, indicating that the selectivity ratio of K+/Na+ was at least 10:1. Channel open probability (P-o) in inside-out patches was 0.12 at 0 mV and was increased by hyperpolarization. The voltage-dependent P-o was fitted with the Boltzmann's equation: P-o = 1/[1 + exp(V - V-1/2)zF/RT], with z = 1.2 and V-1/2 = -40 mV Addition of 2 mM tetraethylammonium or 500 mM quinidine to the bath blocked the activity of the Kf channel in inside-out patches. In addition, decrease in the bath pH from 7.40 to 6.70 reduced P-o by 30%. Addition of the catalytic subunit of protein kinase A (PKA(c); 20 U/ml) and 100 mM MgATP to the bath increased P, from 0.12 to 0.49 at 0 mV and shifted the voltage dependence curve of channel activity toward more positive potentials by 40 mV. Two exponentials were required to fit both the open-time and the closed-time histograms. Addition of PKA, increased the long open-time constant and shortened the long closed-time constant. In conclusion, PKA-mediated phosphorylation plays an important role in the regulation of the voltage dependence of the hyperpolarization-activated K+ channel in the basolateral membrane of CCD. |
| Document Type: Article |
| Language: English |
| Reprint Address: WANG, WH (reprint author), NEW YORK MED COLL, DEPT PHARMACOL, BSB ROOM 501, VALHALLA, NY 10595 USA |
| Publisher: ROCKEFELLER UNIV PRESS, 222 E 70TH STREET, NEW YORK, NY 10021 |
| Subject Category: Physiology |
| IDS Number: RK526 |
| ISSN: 0022-1295 |
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