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First published online November 13, 2009
Journal of Experimental Biology 212, 3873-3881 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.034579

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The intestinal response to feeding in seawater gulf toadfish, Opsanus beta, includes elevated base secretion and increased epithelial oxygen consumption

J. R. Taylor^* and M. Grosell

Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA

^* Author for correspondence (jtaylor{at}rsmas.miami.edu)

Accepted 8 September 2009

Intestinal HCO₃^– secretion is essential to marine teleost fish osmoregulation and comprises a considerable source of base efflux attributable to both serosal HCO₃^– and endogenous CO₂ hydration. The role of intestinal HCO₃^– secretion in dynamic acid—base balance regulation appears negligible in studies of unfed fish, but evidence of high intestinal fluid [HCO₃^–] in fed marine teleosts led us to investigate the source of this HCO₃^– and its potential role in offsetting the postprandial ‘alkaline tide’ commonly associated with digestion. Specifically, we hypothesized that elevated metabolic rate and thus endogenous CO₂ production by intestinal tissue as well as increased transepithelial intestinal HCO₃^– secretion occur post-feeding and offset a postprandial alkaline tide. To test these hypotheses changes in HCO₃^– secretion and O₂ consumption by gulf toadfish (Opsanus beta) isolated intestine were quantified 0, 3, 6, 12, 24 and 48 h post-feeding. Intestinal tissue of unfed fish in general showed high rates of HCO₃^– secretion (15.5 µmol g^–1 h^–1) and O₂ consumption (8.9 µmol g^–1 h^–1). Furthermore, postprandial increases in both intestinal HCO₃^– secretion and O₂ consumption (1.6- and 1.9-fold peak increases, respectively) were observed. Elevated intestinal HCO₃^– secretion rates preceded and outlasted those of O₂ consumption, and occurred at a magnitude and duration sufficient to account for the lack of alkaline tide. The dependence of these high rates of postprandial intestinal base secretion on serosal HCO₃^– indicates transepithelial HCO₃^– transport increases disproportionately more than endogenous CO₂ production. The magnitude of postprandial intestinal HCO₃^– secretion indicates the intestine certainly is capable of postprandial acid#x02014;base balance regulation.

Key words: postprandial, anion exchange, Cl^–/HCO₃^–, NBC, Na⁺/HCO₃^– cotransport, acid#x02014;base balance regulation, alkaline tide

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This article has been cited by other articles:

				J. R. Taylor, E. M. Mager, and M. Grosell Basolateral NBCe1 plays a rate-limiting role in transepithelial intestinal HCO3- secretion, contributing to marine fish osmoregulation J. Exp. Biol., February 1, 2010; 213(3): 459 - 468. [Abstract] [Full Text] [PDF]