PDF OnlyCellular actions of thiazide diuretics in the distal tubule.Stanton, B A Author Information Department of Physiology, Dartmouth Medical School, Hanover, NH 03756. Journal of the American Society of Nephrology : JASN 1(5):p 832-836, November 1990. | DOI: 10.1681/ASN.V15832 Free Metrics Abstract Thiazide diuretics inhibit electroneutral NaCl reabsorption across the distal tubule of the salamander, Amphiuma, and hyperpolarize the basolateral membrane voltage (Vbl) of distal tubule cells. The objective of this study was to determine whether thiazides hyperpolarize Vbl by reducing intracellular Cl- activity (Acl). To this end, distal tubules were perfused in vitro, and electrophysiological techniques were used to measure Acl and Vbl. Hydrochlorothiazide in tubular fluid reduced ACl from 17.0 to 12.6 mM and hyperpolarized Vbl by 16 mV. Reduction of Cl- in tubular fluid from 84 to 8 mM also decreased Acl from 16.1 to 9.9 mM and hyperpolarized Vbl by 12 mV. Because a previous study suggested that electroneutral NaCl reabsorption is mediated by Na+/H(+)-Cl-/HCO3- exchangers in the apical membrane, the Cl-/HCO3- exchange inhibitor, 4,4-diisothiocyanostilbene-2-2-disulphonic acid (DIDS) was added to tubule fluid. DIDS reduced Acl from 15.0 to 11.6 and hyperpolarized Vbl by 10 mV. DIDS and hydrochlorothiazide were not additive, inhibition of Na+/H+ exchange by amiloride (10(-3) M) and Na+ replacement with N-methyl-D-glucamine also reduced Acl from 17.4 to 12.9 and hyperpolarized Vbl by 16 mV. The hyperpolarization of Vbl in each experiment is referable to the fall in Acl. These data show that thiazide diuretics regulate ACl and that the hyperpolarization of Vbl is referable to the thiazide-induced reduction of Acl. Copyright © 1990 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.