Effect of carbenoxolone on alkaline secretion by isolated amphibian gastric and duodenal mucosa.

The influence of carbenoxolone sodium on HCO-3 transport has been examined in spontaneously alkalinizing amphibian antral (Necturus and Rana catesbeiana) and proximal duodenal (Rana catesbeiana) mucosa and in cimetidine-treated fundic mucosa (Rana temporaria) in vivo. Low concentrations of carbenoxolone (10(-6)-10(-4) mol/l, serosal side and 10(-5) mol/l, luminal side) did not affect the secretory rate or electrical properties of these tissues. In the stomach a higher concentration of carbenoxolone (10(-3) mol/l, serosal side) caused an immediate fall in transmucosal potential difference (PD) and electrical resistance. There was an initial decrease in the rate of HCO-3 transport followed by an increase in titratable alkalinization due to passive permeation of base from the serosal bathing solution. The non-steroidal anti-inflammatory agent ibuprofen (3 x 10(-3) mol/l, serosal side) inhibited alkaline secretion while the bile salt sodium taurocholate (10(-4) mol/l, luminal side) converted net alkaline secretion to a titratable acidity in cimetidine-treated fundus. Pretreatment of the mucosa with carbenoxolone (10(-4) mol/l) did not influence the response to taurocholate but when added with ibuprofen it potentiated the inhibitory effect of this drug on fundic alkaline secretion. In contrast, prostaglandin E2 (10(-6) mol/l) markedly reduced the inhibition of fundic alkaline secretion caused by ibuprofen. The anti-ulcer properties of carbenoxolone do not appear to be related to effects on gastroduodenal HCO-3 transport.