AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 4 554-G561, Copyright © 1983 by American Physiological Society
Anomalous potential difference responses to changes in sodium concentration in the antrum of frog stomach
G. Carrasquer, D. Kissel, W. S. Rehm and M. Schwartz
Previously, an electrogenic Na-Cl symport was found in the fundus, and the
question arises of whether there is one in the antrum, a tissue that does
not secrete acid. In an in vitro preparation of the antrum of Rana
catesbeiana, we found that when the [Na+] in nutrient solution was
decreased (choline for Na+) the transmucosal potential difference (PD)
decreased (the positivity of nutrient side decreased), and when the [Na+]
was increased the PD increased. These PD changes were anomalous for Na+ but
not for choline. A linear relationship for PD versus log [Na+] and not
versus log [choline] excluded a choline conductive pathway. The anomalous
PD response was decreased but not abolished by 10(-3) M ouabain. Normal PD
responses resulted from [Na+] changes in Cl--free (SO2-4) solutions. PD
responses to changes in nutrient [Cl-] were normal but decreased in the
absence of Na+. Data are compatible with a passive electrogenic Na-Cl
symport with more chloride than sodium ions transported per cycle, as in
the fundus. Symport conductance-to-total Cl- conductance ratio is higher in
antrum than in the fundus. Data from the luminal side were compatible with
apical membrane conductances for Na+ and Cl-.
