Active alkalinization by amphibian gastric fundic mucosa in vitro.
Gastric fundic mucosae in vitro from four species of frog and Necturus secrete HCO-3 at a steady-state rate of 0.25-0.55  microneq-cm-2-h-1 which corresponds to 5-10% of maximal H+ secretion. Net alkalinization was quantitated in mucosae with spontaneously resting H+ secretion or in mucosae inhibited by histamine H2-receptor antagonists or SNC-. HCO-3 secretion was inhibited by DNP (10(-4) M), CN- (10(-2) M), or anoxia. Acetazolamide inhibited alkalinization at 10(-2) M when added to the nutrient side and at 10(-4) M on the luminal side. Carbachol (10(-4) M) and DBcGMP (10(-4) M) stimulated alkalinization and caused a transient rise in the transmucosal PD; DBcAMP (10(-3) M) was without effect. An almost identical secretion occurred spontaneously in antral mucosae and was insensitive to histamine (10(-5) M). Occurrence in both antral and fundic mucosa suggests that active alkalinization is a property of gastric surface epithelial cells. Gastric alkalinization may protect the luminal surface of the mucosa from the damaging effects of acid and contribute to the continuous removal of H+ ions from gastric contents.
D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001001:Anura; D001639:Bicarbonates / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D003486:Cyanides / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004058:Diffusion; D004140:Dinitrophenols / Q000494:pharmacology; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D006632:Histamine / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D011898:Ranidae; D013861:Thiocyanates / Q000494:pharmacology; D014562:Caudata
D001639:Bicarbonates; D003486:Cyanides; D004140:Dinitrophenols; D006635:Histamine H2 Antagonists; D013861:Thiocyanates; D003994:Bucladesine; D006859:Hydrogen; D006632:Histamine; D002217:Carbachol; D006152:Cyclic GMP; D000086:Acetazolamide