Luminal influences on potassium secretion: chloride, sodium, and thiazide diuretics.
In the presence of Cl-, K+ secretion by the distal tubule saturates with increasing luminal Na+ concentration. Apparent maximal K+ secretion is attained with luminal Na+ concentrations of 40 mM. The results of the present study show that lowering the Cl- concentration of luminal fluid can increase the level of Na(+)-stimulated K+ secretion beyond the maximal level attained in the presence of Cl-. The effect of lowering luminal Cl- concentration to less than 10 mM on K+ secretion is greater with higher Na+ concentration. Under these conditions, chlorothiazide decreases K+ secretion. When chlorothiazide is present, changing the Na+ concentration does not affect K+ secretion. Because in rats a thiazide effect is attributed primarily to the distal convoluted tubule (DCT), we postulate that it is primarily DCT cells that increase K+ secretion when Na+ concentration is raised in the presence of low luminal Cl- concentration. We propose that the rat DCT cells have both an absorptive Na(+)-Cl- cotransport mechanism and a secretory K(+)-Cl- cotransport mechanism in the luminal membrane that can mediate the apparent exchange of Na+ for K+.
Velázquez
H
H
Yale University School of Medicine, New Haven, Connecticut 06510.
Ellison
D H
DH
Wright
F S
FS
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology*; D002740:Chlorothiazide / Q000494:pharmacology; D004232:Diuretics; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D008297:Male; D009994:Osmolar Concentration; D010477:Perfusion; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology*; D049993:Sodium Chloride Symporter Inhibitors / Q000494:pharmacology*; D049992:Sodium Chloride Symporters; D027981:Symporters
D002352:Carrier Proteins; D002712:Chlorides; D004232:Diuretics; D049993:Sodium Chloride Symporter Inhibitors; D049992:Sodium Chloride Symporters; D027981:Symporters; D002740:Chlorothiazide; D012964:Sodium; D011188:Potassium