APStracts 5:0191F, 1998.

Renal sulfate secretion is carbonic anhydrase dependent in a marine teleost, pleuronectes americanus. Renfro, J. Larry, Thomas H. Maren, Cristina Zeien, and Erik R. Swenson,. 1Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269; 2Department of Pharmacology and Therapeutics, University of Florida Health Science Center, Gainesville, Florida 32610; 3Department of Veterans Affairs Medical Center and University of Washington, Seattle, Washington 98108; and 4Mount Desert Island Biological Laboratory, Salsbury Cove, Maine 04672

APStracts 5:0191F, 1998.

Though chemical assays indicate that carbonic anhydrase (CA) activity is present in marine teleost nephrons, CA inhibitors have no effect on urine pH or bicarbonate excretion, parameters typically CA -dependent in almost all vertebrate groups. Because marine teleost renal sulfate secretion is associated with bicarbonate anion exchange, we investigated the effect of CA inhibition on transepithelial sulfate transport by flounder renal tubule primary monolayer cultures (PTCs) and on renal sulfate secretion by intact flounder. Both methazolamide and ethoxzolamide, at 10 _M, inhibited PTC secretory flux approximately 50 %; reabsorptive sulfate flux, Na -dependent glucose transport and transepithelial electrical resistance were unaffected. A CA inhibitor restricted to the extracellular space (10 _M polyoxyethylene-aminobenzolamide, 3.7 kDa) had no effect on PTC sulfate transport. Intravenous administration of methazolamide reduced almost 40% and had no effect on GFR, urine flow rate, or Pi excretion rate. Serum pH was significantly reduced 0.2 units while urine pH was unchanged. Together, the in vitro and in vivo results indicate that CA facilitates renal sulfate secretion in the seawater teleost.

Received 15 June 1998; accepted in final form 22 October 1998
APS Manuscript Number F147-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 10 November 1998