AJP - Renal Physiology, Vol 260, Issue 2 225-F234, Copyright © 1991 by American Physiological Society
Volume regulatory Cl- loss after Na+ pump inhibition in CCT principal cells
K. Strange
Children's Hospital, Division of Nephrology, Harvard Medical School, Boston, Massachusetts 02115.
Ouabain caused rabbit cortical collecting tubule (CCT) principal cells to
swell 53% and then undergo regulatory volume decrease (RVD) at a rate of
4%/min to a new steady-state volume 10% below control. Reduction of
peritubular Cl- concentration transiently depolarized transepithelial
potential (Vte) by 36 mV and stimulated the rate of RVD 30-fold.
Peritubular application of 0.5 mM
4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) inhibited RVD 74%.
In contrast, luminal Cl- reduction or application of DIDS had no effect on
RVD. A 10-fold elevation of perfusate K+ caused volume-regulated cells to
swell 23% at a rate of 60%/min. Removal of luminal Cl- had no effect on
either the rate or magnitude of K+ swelling. Peritubular or bilateral Cl-
removal, however, inhibited the rate of K+ swelling by 96 and 99%,
respectively. Substitution of bath Cl- for Br-, SCN-, or I- inhibited the
rate of K+ swelling by 40, 38, and 98%, respectively. Surprisingly, NO3-
inhibited the rate of K+ swelling by 82%. All Cl- substitutes tested
transiently depolarized Vte by 3-49 mV. These results suggest strongly that
RVD is mediated by a basolateral Cl- channel with a high selectivity for
Cl- over other anions.
