Gastric bicarbonate secretion in humans. Effect of pentagastrin, bethanechol, and 11,16,16-trimethyl prostaglandin E2.
Although the stomach is mainly known for its ability to secrete hydrochloric acid, there is increasing evidence that the gastric mucosa also secretes bicarbonate. A simple method for simultaneous measurement of gastric HCO-3 secretion and H+ secretion was developed from a two-component model of gastric secretion. The method, which is based upon gastric juice volume, H+ concentration, and osmolality, was validated both in vitro and in vivo. In 14 healthy human beings, basal gastric HCO-3 secretion averaged 2.6 mmol/h (range, 0.7-8.7 mmol/h). Basal HCO-3 secretion was approximately 50% of basal H+ secretion and there was a significant correlation between basal HCO-3 and H+ secretion in individual subjects (r = 0.79). HCO-3 was secreted in basal nonparietal secretion at a concentration of approximately 90 mmol/liter. Intravenous pentagastrin infusion markedly stimulated H+ secretion but did not increase HCO-3 secretion. During pentagastrin infusion, the cholinergic agonist, bethanechol, significantly augmented H+ secretion (from 20.2 to 24.7 mmol/h) and increased HCO-3 secretion (from 2.2 to 4.2 mmol/h). A prostaglandin E2 analogue significantly reduced H+ secretion and increased HCO-3 secretion during pentagastrin infusion. The reduction in net gastric juice H+ output following prostaglandin E2 was due more to H+ secretory inhibition than to HCO-3 secretory stimulation. We conclude that the healthy human stomach actively secretes HCO-3 and that gastric HCO-3 secretion can be influenced by cholinergic stimulation and by prostaglandin E2.
D000328:Adult; D018723:Bethanechol; D001626:Bethanechol Compounds; D001639:Bicarbonates / Q000378:metabolism*; D015232:Dinoprostone / Q000031:analogs & derivatives*; D005260:Female; D005744:Gastric Acid / Q000378:metabolism; D005750:Gastric Juice / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D010418:Pentagastrin; D011459:Prostaglandins E, Synthetic
D001626:Bethanechol Compounds; D001639:Bicarbonates; D011459:Prostaglandins E, Synthetic; D018723:Bethanechol; C038879:trimoprostil; D010418:Pentagastrin; D015232:Dinoprostone