Effects of 7-oxa-13-prostynoic acid (7-OPyA) and prostaglandin E1 methyl ester on canine gastric secretion.

The compound 7-OPyA has been reported to antagonize smooth muscle stimulatory effects of some prostaglandins (PG's) in vitro. The in vivo PG antagonist activity of 7-OPyA has not been adequately diarrhea in mice. We studied the effects of this compound on PGE1. Secretion was stimulated by continuous intravenous infusion of histamine. At the steady-state plateau of gastric secretion, PGE1 methyl ester (PGE1 ME) or PGE1 ME and 7-OPyA were simultaneously infused intravenously. The extent of gastric secretory inhibition afforded by PGE1 ME alone or in the presence of 7-OPyA was assessed. 7-OPyA did not modify PGE1 ME gastric antisecretory actions when administered at doses 20-50 times greater than the dose of PGE1 ME. These results suggest that the prostaglandin antagonist effects of 7-OPyA show organ specificity, which may be of clinical importance.