AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 3 208-G212, Copyright © 1980 by American Physiological Society
Mechanisms of electrolyte transport in rat ileum
Y. H. Tai and R. A. Decker
The short-circuit current (Isc), potential difference (PD), tissue
conductance (Gt), and Na and Cl fluxes in the short-circuit state across
rat ileum were studied in Ussing chambers using a variety of bathing
solutions. In Ringer solution, Isc exceeded net Na absorption and net Cl
secretion occurred. Addition of 10 mM glucose increased Isc, PD, Gt, and
net Na absorption, which accounts for 70% of the increase in Isc. Removal
of HCO3 from Ringer solution did not alter any parameters but increased net
Cl secretion due to a decrease in mucosal-to-serosal Cl flux. Reduction by
50% of the [Cl] in HCO3-free solution decreased the net Cl secretion to the
level in Ringer solution and increased net Na absorption. Removal of Cl
decreased Isc to the value of the net Na absorption and decreased the Na
influx across the mucosal membrane by 39%. Isc and PD were near zero and
net Cl absorption was observed in a Na-free solution. These results are
consistent with the transport mechanism that consists of 1) an electrogenic
Na absorptive process that accounts for the Isc, 2) a neutral NaCl-coupled
secretory process, and 3) a system by which HCO3- secretion exchanges for
Cl- absorption.
