AJP - Gastrointestinal and Liver Physiology, Vol 255, Issue 2 247-G252, Copyright © 1988 by American Physiological Society
Effect of pH on chloride absorption in the flounder intestine
A. N. Charney, J. I. Scheide, P. M. Ingrassia and J. A. Zadunaisky
Mount Desert Island Biological Laboratory, Salsbury Cove, Maine 04672.
Chloride absorption in the small intestine of the winter flounder,
Pseudopleuronectes americanus, is reported to be sensitive to ambient pH.
We studied this sensitivity in isolated stripped intestinal mucosa mounted
in modified Ussing chambers. Unidirectional 36Cl fluxes (JClm----s,
JCls----m) were measured under short-circuited conditions in bathing
solutions containing various combinations of HCO3- (0-20 mM), partial
pressure of CO2 (0-36 mmHg), and pH (6.77-7.85). We found that JClm----s,
net 36Cl flux (JClnet), and short-circuit current (Isc) increased and
JCls----m decreased predominately in response to increases in bathing
solution pH. There was a linear relationship between pH and both JClnet (r
= 0.92, P less than 0.01) and Isc (r = 0.96, P less than 0.005) between pH
6.77 and 7.74. The pH effect was completely reversible, did not require
either CO2 or HCO3-, and was not affected by the presence of mucosal barium
at 1 mM. Mucosal bumetanide (0.1 mM) completely inhibited the pH effect.
These data suggest that the process by which Cl- is absorbed in the
flounder intestine is sensitive to pH. The data do not indicate whether pH
affects Na+-K+-2Cl- cotransport or a Cl- transport pathway in series with
this process. The direction of Cl- absorption in response to pH contrasts
with inverse relation of pH and Cl- absorption in mammalian small
intestine.
