Two types of K(+) channels at the basolateral membrane of proximal tubule: inhibitory effect of taurine.

The cell-attached configuration of the patch-clamp technique was used to investigate the effects of taurine on the basolateral potassium channels of rabbit proximal convoluted tubule. In the absence of taurine, the previously reported ATP-blockable channel, K(ATP), was observed in 51% of patches. It is characterized by an inwardly rectifying current-voltage curve with an inward slope conductance of 49 +/- 5 pS (n = 15) and an outward slope conductance of 13 +/- 6 pS (n = 15). The K(ATP) channel open probability (P(o)) is low, 0.15 +/- 0.06 (n = 15) at a -V(p) = -100 mV (V(p) is the pipette potential), and increases slightly with depolarization. The gating kinetics are characterized by one open time constant (tau(o) = 5.0 +/- 1.9 ms, n = 6) and two closed time constants (tau(C1) = 5. 2 +/- 1.5 ms, tau(C2) = 140 +/- 40 ms; n = 6). In 34% of patches, a second type of potassium channel, sK, with distinct properties was recorded. Its current-voltage curve is characterized by a sigmoidal shape, with an inward slope conductance of 12 +/- 2 pS (n = 4). Its P(o) is voltage independent and averages 0.67 +/- 0.03 (n = 4) at -V(p) = -80 mV. Both its open time and closed time distributions are described by a single time constant (tau(o) = 96 +/- 19 ms, tau(C) = 10.5 +/- 3.6 ms; n = 4). Extracellular perfusion of 40 mM taurine fails to affect sK channels, whereas K(ATP) channel P(o) decreases by 75% (from 0.17 +/- 0.06 to 0.04 +/- 0.02, n = 7, P < 0.05). In conclusion, the absolute basolateral potassium conductance of rabbit proximal tubules is the resulting combination of, at least, two types of potassium channels of roughly equal importance: a high-conductance low-open probability K(ATP) channel and a low-conductance high-open probability sK channel. The previously described decrease in the basolateral absolute potassium conductance by taurine is, however, mediated by a single type of K channel: the ATP-blockable K channel.

[1]  N. Anzai,et al.  Potassium transport and potassium channels in the kidney tubules. , 1997, The Japanese journal of physiology.

[2]  R. Laprade,et al.  Inhibition of basolateral potassium conductance by taurine in the proximal convoluted tubule. , 1996, The American journal of physiology.

[3]  R. Laprade,et al.  Cell volume increases of physiologic amplitude activate basolateral K and CI conductances in the rabbit proximal convoluted tubule. , 1996, Journal of the American Society of Nephrology : JASN.

[4]  W. Ho,et al.  Blockade of the ATP-sensitive potassium channel by taurine in rabbit ventricular myocytes. , 1996, Journal of molecular and cellular cardiology.

[5]  H. Satoh.  Direct inhibition by taurine of the ATP-sensitive k+ channel in guinea pig ventricular cardiomyocytes. , 1996, General pharmacology.

[6]  S. Silbernagl,et al.  Compartmentation of amino acids in the rat kidney. , 1996, The American journal of physiology.

[7]  P. Welling.  Cross-talk and the role of KATP channels in the proximal tubule. , 1995, Kidney international.

[8]  E. Schlatter,et al.  K+ channels in the basolateral membrane of rat cortical collecting duct. , 1995, Kidney international.

[9]  R. Laprade,et al.  Hypotonicity increases basolateral taurine permeability in rabbit proximal convoluted tubule. , 1995, The American journal of physiology.

[10]  W. Wang,et al.  Two types of K+ channel in thick ascending limb of rat kidney. , 1994, The American journal of physiology.

[11]  T. Dubose,et al.  ATP-sensitive K(+)-selective channels of inner medullary collecting duct cells. , 1994, The American journal of physiology.

[12]  R. Laprade,et al.  Coupling between transepithelial Na transport and basolateral K conductance in renal proximal tubule. , 1994, The American journal of physiology.

[13]  R. Chesney,et al.  Polarity of taurine transport in cultured renal epithelial cell lines: LLC-PK1 and MDCK. , 1993, The American journal of physiology.

[14]  R. Laprade,et al.  Na+ pump inhibition downregulates an ATP-sensitive K+ channel in rabbit proximal convoluted tubule. , 1993, The American journal of physiology.

[15]  R. Laprade,et al.  Regulation of basolateral K channels in proximal tubule studied during continuous microperfusion. , 1993, The American journal of physiology.

[16]  G. Giebisch,et al.  Vasopressin increases density of apical low-conductance K+ channels in rat CCD. , 1993, The American journal of physiology.

[17]  G. Giebisch,et al.  Involvement and source of calcium in volume regulatory decrease of collapsed proximal convoluted tubule. , 1992, The American journal of physiology.

[18]  G. Giebisch,et al.  ATP is a coupling modulator of parallel Na,K-ATPase-K-channel activity in the renal proximal tubule. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[19]  G. Giebisch,et al.  Dual effect of adenosine triphosphate on the apical small conductance K+ channel of the rat cortical collecting duct , 1991, The Journal of general physiology.

[20]  G. Giebisch,et al.  A potassium channel in the apical membrane of rabbit thick ascending limb of Henle's loop. , 1990, The American journal of physiology.

[21]  L. Garneau,et al.  Membrane crosstalk in the mammalian proximal tubule during alterations in transepithelial sodium transport. , 1990, The American journal of physiology.

[22]  L. Palmer,et al.  Low-conductance K channels in apical membrane of rat cortical collecting tubule. , 1989, The American journal of physiology.

[23]  R. Sauvé,et al.  Single-channel analysis of a K channel at basolateral membrane of rabbit proximal convoluted tubule. , 1988, The American journal of physiology.

[24]  H. Sackin.  Stretch-activated potassium channels in renal proximal tubule. , 1987, The American journal of physiology.