Gastric antisecretory actions of (15S)-15-methyl prostaglandin E2 methyl ester and natural prostaglandin E2 in rhesus monkeys

An unexpected potent positive chronotropic effect of (15S)-15-methyl-prostaglandin E1 in the isolated guinea-pig right atria

The effects of (15S)-15-methyl-prostaglandin E1, a synthetic analog of PGE1, other stable prostaglandins, histamine and noradrenaline were studied on the isolated spontaneously beating right atria from guinea-pig, rat and rabbit. When compared with other prostaglandins, histamine and noradrenaline, 15-methyl analog of PGE1 has the most potent positive chronotropic effect and the highest affinity as indicated by a significantly higher pD2 value as compared to other tested analogs in the isolated guinea-pig right atria. Neither the 15-methyl analog of PGE1 nor other stable prostaglandins induced any effect on the atria from rat and rabbit when relatively higher concentrations were used. 15-Methyl-PGE1 did not induce a positive inotropic effect. The maximum positive chronotropic response to 15-methyl-PGE1 was found to be about 60% of that of noradrenaline and histamine but almost equal to that of PGE1. These results were taken as evidence that 15-methyl-PGE1 has an unexpected potent positive chronotropic effect on the isolated spontaneously beating guinea-pig right atrium. The possible mechanism of the action of 15-methyl-PGE1 are discussed.

Oral antisecretory activity of prostaglandin E2 in man

We studied the oral gastric antisecretory activity of prostaglandin E2 in three groups of six normal volunteers. Each volunteer was studied twice, once after receiving prostaglandin E2 (0.5, 1.0, or 2.0 mg) and the other time after receiving placebo administered in a double-blind, randomized fashion. Gastric acid secretion was stimulated with a liquid protein meal from 1/2 to 1 1/2 hr after drug administration. Acid secretion was quantitated using the technique of intragastric titration. Acid secretion after 0.5 mg of prostaglandin E2 was no different than after placebo administration, but 1.0 mg and 2.0 mg of prostaglandin E2 inhibited 58% (6.68 +/- 7.64 meq vs 14.67 +/- 6.75 meq, P less than 0.02) and 76% (2.38 +/- 2.38 meq vs 11.50 +/- 3.51, P less than 0.01) respectively, of gastric acid production compared to placebo therapy. After oral administration, prostaglandin E2 in man is antisecretory with an ED50 of 1.1 mg.

Endogenous prostaglandins in peptic ulcer disease

Plasma concentrations of prostaglandins E and F have been measured by radioimmunoassay in patients undergoing diagnostic upper intestinal endoscopy. The results fail to support a previously reported deficiency of plasma PGE in duodenal ulcer patients. Plasma prostaglandin concentrations failed to correlate with the parameters of gastric secretion studied; and were unaffected by histamine H2-receptor blockade or the activity of duodenal ulceration. During combined pentagastrin and insulin secretory studies there was a significant correlation between the outputs of PGE and acid into gastric juice.