APStracts 5:0074F, 1998.

Low nacl diet increases h-k atpase in intercalated cells from rat cortical collecting duct. Silver, Randi B., Han Choe, and Gustavo Frindt. Department of Physiology, Cornell University Medical College, New York, New York 10021

APStracts 5:0074F, 1998.

Extracellular K+- dependent H+ extrusion after an acute acid load, an index of H-K exchange, was monitored in intercalated cells (ICs) from rat cortical collecting tubule (CCT) using ratiometric fluorescence imaging of the intracellular pH (pHi) indicator, 2',7' -bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The hypothesis tested was that 10-14 day NaCl deprivation increases H-K ATPase in rat ICs. The rate of H-K exchange in the low NaCl ICs was double that of controls. In control ICs H-K exchange was inhibited by SCH 28080 (10 mM). In the low NaCl ICs it was partially blocked by SCH 28080 or ouabain (1 mM). Simultaneous addition of both inhibitors abolished K -dependent pHi recovery. The induced H-K exchange observed with NaCl restriction was not due to elevated plasma aldosterone as evidenced by experiments on ICs from rats implanted with osmotic mini-pumps administering aldosterone such that plasma levels were comparable to those of NaCl deficient rats. The results suggest that NaCl deficiency induces two isoforms of H-K ATPase in ICs and that this effect is not mediated by elevated plasma aldosterone.

Received 28 July 1997; accepted in final form 12 March 1998.
APS Manuscript Number F251-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 6 April 1998