title: Evidence for rheogenic sodium bicarbonate cotransport in the basolateral membrane of oxyntic cells of frog gastric fundus.
abstract: Ionic conductance properties of the basolateral cell membrane of oxyntic cells were studied in frog gastric fundus in vitro. After mounting the fundus in a modified Ussing chamber the serosal connective tissue was dissected off and individual oxyntic cells were punctured from the serosal surface with microelectrodes. Under resting conditions the membrane potential averaged -56.9, SD +/- 9.5 mV (n = 63), cytoplasm negative. Lowering or raising serosal HCO-3 concentration from 17.8 to 6 or 36 mmol/l respectively at constant PCO2 depolarized or hyperpolarized the cell membrane by +16.7 or -18.2 mV respectively. Sudden removal of serosal Na+ also depolarized the cell membrane (anomalous Nernst response). Since both the HCO-3 dependent and the Na+ dependent potential changes were strongly depressed by the disulfonic stilbene SITS and since the potential response to HCO-3 was virtually abolished in Na+-free solution we conclude that a rheogenic Na+ (HCO-3)n-cotransport system (n greater than 1) is present in the basolateral cell membrane of oxyntic cells. Its possible role in base transfer during HCl-secretion or HCO-3 secretion remains to be elucidated.
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism*; D004553:Electric Conductivity; D005748:Gastric Fundus / Q000378:metabolism / Q000648:ultrastructure*; D010295:Parietal Cells, Gastric / Q000378:metabolism / Q000648:ultrastructure*; D011893:Rana esculenta; D012212:Rheology; D012704:Serous Membrane / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D017693:Sodium Bicarbonate
chemical_list: D001639:Bicarbonates; D017693:Sodium Bicarbonate; D012964:Sodium