HCO3 transport in rat jejunum: relationship to NaCl and H2O transport in vivo.
- 1 January 1977
- journal article
- Published by American Physiological Society in American Journal of Physiology-Endocrinology and Metabolism
- Vol. 232 (1), E62-8
- https://doi.org/10.1152/ajpendo.1977.232.1.e62
Abstract
HCO3- absorption and its association with Na+ absorption has been studied in the rat jejunum in vivo, using a single-pass perfusion technique. The method of disequilibrium pH, the only valid way of demonstrating jejunal H+ secretion, was used to distinguish between an HCO3- pump and H+ secretion as the mechanism of HCO3- absorption. HCO3- stimulated Na+ absorption; Na+ deletion inhibited HCO3 absorption, decreased luminal acidification, and decreased the level of luminal PCO2. These results confirmed an Na+:H+ cation exchange, the possible mechanism of which is discussed in terms of results using other tissues. Na+-dependent HCO3-absorption made up a larger part of total HCO3-absorption as the luminal HCO3-concentrations diminished, although the precise degree of Na+-dependency could not be determined because of the unstirred layer effect. The mechanism of Na+-independent HCO3-absorption was not established, but it was not affected by PD, Cl-, or H2O movements. Glucose-stimulated and HCO3-stimulated Na+ absorption were less than additive. The physiological importance of HCO3-stimulated Na+ absorption in the acidic postprandial jejunum is probably due entirely to the effect of free CO2 in the lumen.Keywords
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