Effect of ouabain and furosemide on pepsinogen secretion by gastric glands in vitro

Gastric glands were isolated from rabbit stomach and pepsinogen secretion was measured after stimulation with isoproterenol, forskolin, 8-bromo cyclic adenosine monophosphate (8-bromo cAMP), cholecystokinin octapeptide (CCK-OP), carbachol, and hyperosmolar medium. The responses to these stimuli in medium containing 143 mM Na+ and 5.4 mM K+ (normal medium) were compared with responses to the same stimuli in media containing either 0 Na+ and 5.4 mM K+, or 143 mM Na+ and O K+. In addition, the effects of ouabain and furosemide on secretion elicited by these stimuli were determined. Medium containing 0 Na+ inhibited all stimuli. Medium containing 0 K+ inhibited the action of 8-bromo cAMP and stimuli postulated to be mediated by cAMP. Ouabain inhibited the same stimuli as O K+ medium, and, in addition, inhibited the response to hyperosmolar medium. However, ouabain enhanced the response to CCK-OP. Furosemide inhibited the response to hyperosmolar medium but had no effect on the action of any secretagogue employed. Intraglandular [Na+] increased and [K+] decreased after exposure to K+-free medium or ouabain. cAMP content of the glands was assayed after stimulation with both isoproterenol and hyperosmolar medium. Isoproterenol and hyperosmolar medium significantly increased cAMP levels. The results are discussed in relation to possible involvement of ion transport or intracellular ion concentration in the secretory process.