K+ selectivity and HCl secretion in Xenopus and their relation to cAMP and Ba2+.
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.
D000818:Animals; D001464:Barium / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D005753:Gastric Mucosa / Q000378:metabolism / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D014981:Xenopus / Q000502:physiology*
D001464:Barium; D000242:Cyclic AMP; D011188:Potassium