Characterization of aldosterone-induced potassium secretion in rat distal colon.
The role of apical and basolateral membranes in aldosterone-induced active potassium (K) secretion in rat distal colon was investigated by measuring mucosal-to-serosal (Jms) and serosal-to-mucosal (Jsm) 42K fluxes (mueq.h-1.cm-2) across isolated stripped mucosa under short-circuit conditions in normal and secondary-hyperaldosterone animals. In normal colons mucosal tetraethylammonium (TEA; 30 mM) or barium (Ba; 5 mM), but not cesium (Cs; 15 mM), reduced Jsm without affecting Jms. In aldosterone animals (a) net K secretion (-0.54 +/- 0.11) was converted to net K absorption (0.63 +/- 0.15) by mucosal TEA, which produced a marked reduction in Jsm (0.82 +/- 0.07) and an increase in Jms (0.35 +/- 0.07). In contrast mucosal Ba resulted in a relatively smaller reduction in JK(sm) without altering JK(ms), whereas mucosal Cs was ineffective; (b) serosal bumetanide or the removal of serosal Na or Cl markedly inhibited JK(sm and abolished net K secretion; and (c) serosal ouabain (1 mM) produced qualitatively similar effects to those of serosal bumetanide. These results demonstrate that (a) normal rat distal colon contains apical TEA- and Ba-sensitive K channels; (b) aldosterone induces TEA-sensitive and Ba-sensitive apical K channels; (c) aldosterone-induced K secretion requires both the Na,K-pump and Na-K-2Cl cotransport for K uptake across the basolateral membrane; and (d) alteration of any of these processes results in inhibition of aldosterone-induced active K secretion simultaneously with stimulation of K absorption.
Sweiry
J H
JH
Department of Internal Medicine, Yale University, New Haven, Connecticut 06510.
Binder
H J
HJ
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D002586:Cesium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D002712:Chlorides; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D002034:Bumetanide; D002586:Cesium; D001464:Barium; D000450:Aldosterone; D010042:Ouabain; D019789:Tetraethylammonium; D012964:Sodium; D011188:Potassium