AJP - Gastrointestinal and Liver Physiology, Vol 240, Issue 4 331-G337, Copyright © 1981 by American Physiological Society
K+ selectivity and HCl secretion in Xenopus and their relation to cAMP and Ba2+
N. Takeguchi, Y. Nishimura, M. Morii, I. Horikoshi and S. Inoue
Doses of 1, 5, and 10 mM adenosine 3',5'-cyclic monophosphate (cAMP)
applied to previously resting Xenopus gastric mucosae initiated a
dose-dependent acid secretory response. Increases in the K+ concentration
of the submucosal solution. [K+sm], resulted in higher acid secretory rates
and concomitant lower transmucosal resistances at the indicated cAMP
concentration. The transmucosal potential difference, PD, had a liner slope
against log [K+sm] over the range of 20-80 mM K+sm. Values of the slope (K+
selectivity, -PD/log[K+sm]) were less than 26 mV/log for resting mucosae,
and in the range of 29-58 mV/log for both spontaneously secreting and
cAMP-stimulated mucosae. These values were dose dependent on the cAmP
concentration. In the presence of 10 mM Ba2+ together with cAMP, the K+
selectivity and the H+ secretory rate decreased compared with the case of
cAMP only.
