The syntheses of 2-oxo-1,8-naphthyridine-3-carboxylic acid derivatives having potent gastric antisecretory properties in the pyloric-ligated (Shay) rat model are described. Two of the more potent compounds tested that were selected for more detailed dose-response evaluation were 4-amino-1-ethyl-1,2-dihydro-2-oxonaphthyridine-3-carboxylic acid ethyl ester (35) and 1-ethyl-1,2-dihydro-7-methyl-4-(4-methyl-1-piperazinyl)-2- oxo-1,8-naphthyridine-3-carboxylic acid ethyl ester (77). These compounds lowered total acid output in the rat in a dose-related fashion. Both compounds were more potent than cimetidine when tested in the rat. Both 35 and 77 showed inhibitory activity in food-stimulated acid secretion in the Pavlov-pouch, conscious dog. The mechanism of action for this series is not known. Details of structure-activity relationships are described.

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Misoprostol, a synthetic derivative of prostaglandin E1, was tested and shown to be an effective gastric antisecretory agent against histamine-, pentagastrin-, and meal-stimulated acid secretion in dogs. Misoprostol reduced the volume of acid secretion as well as the hydrogen ion concentration. Misoprostol did not reduce gastric mucosal blood flow, nor did it alter meal-stimulated serum gastrin levels. Misoprostol inhibited acid secretion in histamine-stimulated isolated gastric glands indicating a direct antisecretory effect on parietal cells. The potency of misoprostol was greatest when administered in direct contact with the gastric mucosa indicating local absorption and action. Misoprostol strengthened the gastric mucosal barrier as shown by the attenuation of aspirin-induced lowering of transmucosal electrical potential differences. Misoprostol protected the gastric mucosa of rats subjected to ethanol-, taurocholate-, pyloric ligation-, stress- and indomethacin-induced damage. Misoprostol also protected against indomethacin-induced intestinal lesions in rats and reduced duodenal ulcer formation in guinea-pigs and cats. The doses of misoprostol required to protect against gastric damage were about one-tenth of those required to inhibit acid secretion. The results of these and other studies indicate that misoprostol is a safe agent with unique properties that should provide a new approach for treatment of ulcer diseases of the gastrointestinal tract.

The polymerization of isobutene in ethyl chloride solution at -78.5 "C has been studied using stannic chloride as catalyst and alkyl substituted phenols as cocatalysts. In preliminary experiments, the nature and extent of the complexing between phenols and stannic chloride was examined and it was shown that G-complexing occurs between the oxygen of the phenol and the stannic chloride. Equilibrium constants were determined over the temperature range 30 to -50 "C and were used, together with hydrogen bonding data, to estimate the concentrations of complex and free phenol in the polymerization mixtures at -78.5 "C. The active initiator in the polymerization is probably the G-complex but the free phenol acts as a chain terminating agent. This explains the ability of the cocatalyst to decrease the rate of polymerization under some experimental conditions. For isobutene concentrations up to 3 M and at constant dielectric constant the rate of polymerization and the molecular weight are proportional to the monomer concentration. A mechanism is proposed to account for the main features of the experimental results.

Isolated canine parietal cells were used to study the ability of misoprostol to inhibit acid secretion in the presence of a number of acid secretagogues. Misoprostol inhibited histamine-stimulated acid secretion in a dose-dependent and noncompetitive manner. A concentration of 2-3 X 10(-9) M misoprostol inhibited maximal histamine-stimulated acid secretion by one half. Misoprostol had little to no effect on acid secretion stimulated by carbachol and dibutyryl cAMP, had no effect on the acid secretion directly stimulated by pentagastrin, and only modestly inhibited acid secretion stimulated by forskolin. Misoprostol noncompetitively inhibited cAMP formation in response to histamine, with an IC50 value similar to that for the inhibition of histamine-stimulated acid secretion. These results indicate that: (1) misoprostol specifically inhibits histamine-stimulated acid secretion in parietal cells, and (2) the antisecretory action of misoprostol is closely related to the reduction of histamine-stimulated cAMP formation with the site of major action most likely in the coupling process between histamine H2 receptor sites and histamine-sensitive adenylate cyclase.