AJP - Gastrointestinal and Liver Physiology, Vol 240, Issue 4 267-G273, Copyright © 1981 by American Physiological Society
Origins of positive potential difference of frog gastric mucosa in Cl--free solutions
M. Schwartz, T. C. Chu, G. Carrasquer, W. S. Rehm and T. L. Holloman
Experiments were performed on gastric mucosae of Rana pipiens with an in
vitro method. Bathing both sides of the mucosae in Cl--free solutions
resulted in an inverted potential difference (PD) (i.e., nutrient
negative). Cimetidine in a concentration of 10(-4) or 10(-3) M in the
nutrient solution gave a positive PD when the H+ secretory rate was zero or
near zero and confirmed that the PD versus H+ rate was linear. the origins
of the positive PD were examined by ion replacement, e.g., choline for Na+
in both solutions. When both solutions had 25 mM HCO(-)3 (i.e., no HCO(-)3
gradient), the difference in PD between choline sulfate and Na2SO4
solutions indicated a possible small active transport of Na+ from the
secretory to nutrient side. Similar experiments indicated no active K+
transport. A residual PD occurred without Na+. With H+ rate zero, 100% O2,
and no HCO(-)3, a base secretion of about 0.4 mueq.h-1.cm-2 was obtained in
a direction to contribute to the positive PD. Active SO2(-)4 transport may
occur.
