Biphasic effect of angiotensin ii on intracellular sodium concentration in rat proximal tubules. Reilly, Angela M., Peter J. Harris, and David A. Williams. Department of Physiology, The University of Melbourne, Parkville, 3052, Victoria, Australia.
APStracts 2:0064F, 1995.
Intracellular Na+ concentration [Na+]i was determined using ratiometric measurement of the Na+-sensitive fluorescent probe, sodium-binding benzofuran isophthalate (SBFI). Angiotensin II (ANG II - 10-11 to 10-7M), applied to the basolateral membrane of rat isolated proximal convoluted tubules, induced a rapid and reversible dose-dependent increase in [Na+]i which was initiated within 300 msec. A maximal response was observed over the range 10-9 to 10-7M ANG II, with an average increase in [Na+]i of 7.4 1.0mM. At higher concentrations (10-6 to 10-5M) ANG II decreased [Na+]i compared with control (14.2 0.6mM). The increase in [Na+]i induced by 10-9M ANG II was attenuated by inhibiting the Na+/H+ antiporter with clonidine whereas HOE 694, a specific blocker of the NHE-1 isoform of the Na+/H+ exchanger, had no effect. The increase in [Na+]i induced by 10-9M ANG II was enhanced by inhibition of the Na+-HCO-3 cotransporter with H2-DIDS, with an average increase in [Na+]i of 17.1 6.6mM. The data provide direct, high time resolution measurements of the effects of ANG II on intracellular sodium concentration in the proximal tubule, and support the proposition that an increase in transepithelial sodium reabsorption by ANG II involves stimulation of both a Na+/H+ exchanger and the Na+-HCO-3 cotransporter. 

Received 1 November 1994; accepted in final form 7 April 1995.
APS Manuscript Number F388-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  2 May 1995.