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Indomethacin produces gastric corpus erosions in the fasted rat and small intestinal ulcers in the conventionally fed rat. We found that in rats fed chow pellets for 1 h after a 24-h fast, indomethacin given within 2 h after refeeding produced lesions in the gastric antrum, primarily along the lesser curvature, and also in the small intestine. The antral lesions reached a maximum size in 6–10 h, penetrated the muscularis mucosae within 3 days, and did not diminish for at least 7 days. The formation of the antral ulcer was prevented by prostaglandins or adrenalectomy, but was not affected by cimetidine, atropine, and/or vagotomy. In contrast, the gastric corpus erosions produced by indomethacin in the fasted rat were prevented by antisecretory drugs or vagotomy, and were aggravated by adrenalectomy. It is concluded that: (a) the chronic antral ulcers produced by indomethacin in the refed rat mimic human gastric ulcer with regard to location and histology; and (b) the mechanism of antral ulcer formation is different from corpus erosion formation, in that it was resistant to antisecretory drugs and vagotomy and was prevented by adrenalectomy. This experimental ulcer model could prove useful for studies of the etiology and therapy of gastric ulcer disease.

2-Mono-and 2, 6-di-substituted cAMP (cAMP : adenosine 3', 5'-cyclic phosphate) were derived from the corresponding adenosine analogs via the 5'-phosphates. 2-Substituted cAMP and aristeromycin 3', 6'-cyclic phosphate were led to the 8-bromo derivatives. 8-(3, 5-Dimethylpyrazol-1-yl)-cAMP was derived from 8-hydrazinoadenosine. 8-(2-Hydroxypropyl-2)-cAMP was prepared by a γ-ray irradiation of cAMP in isopropanol. N6-Butyl-2-phenyl-cAMP was derived from 2-phenylinosine. 2-or 8-Substituted cAMP was led to its dibutyryl derivative. The activities of these new analogs were assessed with cAMP-dependent protein kinases (PK) and cAMP phosphodiesterases (PDE). 8-Bromo-2-chloro-, 2-chloro-, 2-bromo-, 2-phenylthio-, 8-carbamoyl- and 8-carboxy-cAMP were better activators of PK than cAMP, while 2-substituted analogs were significant substrates and inhibitors of PDE. 2-Phenyl-, benzyl-, phenoxy-, chloro- and bromo-cAMP or aristeromycin 3', 6'-cyclic phosphate had an inhibitory effect on the binding of cAMP to PK equal to or more than cAMP.

The protective effect of spizofurone (AG-629) on the rat gastric mucosa was studied in the presence of various stimuli. Spizofurone given orally markedly inhibited gastric lesions induced by ethanol (ED 50 = 6.5 mg/kg). Spizofurone inhibited ethanol-induced gastric lesions even when administered intraperitoneally (i.p.), but the onset of action after oral administration was shorter. Spizofurone given orally or i.p. in a dose range of 25–200 mg/kg inhibited indomethacin-induced gastric antral ulcers in re-fed rats. Furthermore, spizofurone potentiated the inhibitory effect of prostaglandin E 2 on indomethacin-induced gastric antral ulcers. Spizofurone given i.p. prevented a decrease in potential difference and the formation of gastric lesions induced by intragastric instillation of 30 mM aspirin in 0.1 N HCl. Spizofurone given i.p. inhibited the increase in net fluxes of H + and Na + caused by intragastric instillation of 15% ethanol in 0.1 N HCl. These findings indicate that spizofurone, like prostaglandin E 2 , exerts gastric mucosal protection and even potentiates the anti-ulcer effect of prostaglandin E 2 . The gastric mucosal protection by spizofurone is ascribed in part to preservation of the mucosal barrier.

The metabolites of 6-ethyl-3-(1H-tetrazol-5-yl)chromone (AA-344) (1), an orally effective antiallergic agent, and their analogues were synthesized to confirm the proposed structures and to determine their activity in the rat passive cutaneous anaphylaxis (PCA) test. A glucuronic acid metabolite (6) was assigned the structure 24b, 1-deoxy-1-[5-(6-ethylchromon-3-yl)tetrazol-1-yl]-beta-D-glucopyranuronate, by the comparison of 13C NMR, mass spectra, and TLC of isomeric compounds. In 13C NMR spectra, the shift difference of the tetrazole ring carbons between a pair of isomers was more remarkable than that of the glycosidic carbons. Therefore, the former is a useful criterion for distinguishing between such isomers. Some of the metabolities and analogues were active when administered intravenously, and two metabolites (2 and 3) were also effective upon oral administration.

AA-2379 (methyl 7-butyl-4,5,6,7-tetrahydro-3-methylamino-4,6-dioxo-5-propyl- 2H-pyrazolo [3,4-d]pyrimidine-2-carboxylate) has antiinflammatory, analgesic, and antipyretic activities, and inhibits the type III allergic (Arthus) reaction. In the studies reported here, we investigated the effect of AA-2379 on rat polymorphonuclear leukocyte (PMN) functions to clarify the mechanism of the antiinflammatory and antiallergic actions of AA-2379. AA-2379 at 10(-4) M inhibited lysozomal enzyme release. AA-2379 inhibits formyl methionyl-leucyl-phenylalanine (fMLP)- and C5a-induced arachidonic acid release; their 50% inhibitory concentrations were 2.8 x 10(-5) and 3.8 x 10(-5) M, respectively. Because dibutyryl cAMP, a cAMP analogue, and 3-isobutyl-1-methylxanthine, a cAMP phosphodiesterase inhibitor, inhibited fMLP-induced arachidonic acid release, and AA-2379 inhibited cAMP phosphodiesterase and increased cAMP content in PMNs, it is likely that AA-2379 inhibited arachidonic acid release by increasing cAMP content in rat PMNs. Furthermore, from the studies of fMLP-induced arachidonic acid release in Ca free medium it is suggested that AA-2379 inhibits the process which depends on Ca concentration in the medium. These results suggest that the inhibitory effect of AA-2379 on inflammation and allergic reactions such as the Arthus reaction is partly exerted by inhibiting PMN functions such as arachidonic acid and lysozomal enzyme release.

In studies of the role of leukotrienes in inflammatory reactions, the induction of rat reversed passive Arthus pleurisy (a type III allergic reaction) was employed. Increases of exudate volume, vascular permeability, and migration of inflammatory cells in the pleural cavity were observed. The vascular permeability was enhanced biphasically during 0–30 min (early response) and during 3–6 h (late response) after induction of the pleurisy. The infiltration of inflammatory cells, mainly polymorphonuclear leukocytes, into the cavity increased and reached a maximum 6 h after the pleurisy was induced. Leukotriene B4 (LTB4), 5-monohydroxyeicosatetraenoic acid (5-HETE), and slow-reacting substance of anaphylaxis (SRS-A), consisting of LTC4, LTD4 and LTE4, were detected in the exudate by reversed-phase high-performance liquid chromatography during the early response. The contents of LTC4 reached a maximum 10 min after the challenge, followed by a rapid decrease within 1 h. The rise and decay of LTC4 correlated with the increase in vascular permeability during the early phase. AA-861, a 5-lipoxygenase inhibitor, given intrapleurally inhibited the increase in vascular permeability, cell migration, and generation of leukotrienes during the early phase of the pleurisy. These results indicate that products of the 5-lipoxygenase pathway, such as LTC4 and LTB4, may play an important role as chemical mediators in the inflammatory reaction.

Amoxanox has potent antiallergic activity because it inhibits the release of chemical mediators such as histamine and leukotrienes. We studied the in vitro effect of amoxanox on arachidonic acid metabolism, including the lipoxygenase and cyclooxygenase pathways. Amoxanox inhibited calcium ionophore A23187-induced formation of 5-HETE, LTB4, SRS-A (LTC4, LTD4 and LTE4), and 12-HETE in rat peritoneal resident monocytes. These results indicate that amoxanox inhibits 5- and 12-lipoxygenases. The compound, however, did not affect the formation of TXB2 or 6-keto-PGF1α in guinea pig lung fragments and PGE2 or PGF2α in bovine seminal vesicles, suggesting that it did not inhibit cyclooxygenase. These results show that the antiallergic action of amoxanox is associated, at least in part, with the reduction of leukotrienes due to the inhibition of lipoxygenases.

A newly synthesized compound, 6-ethyl-3-(1H-tetrazol-5-yl)chromone (AA-344) given intravenously or orally inhibited considerably the 72-hr passive cutaneous anaphylaxis (72-hr PCA) induced by IgE in rats. The antiallergic action of AA-344 was neither due to the antihistamine or antiserotonin effect nor was it mediated via adrenergic mechanisms. The results obtained in a double sensitization with two IgE antibodies suggest that AA-344 may not impair antigen-antibody combination but probably prevents the release of chemical mediators including histamine. This assumption was supported by observation that AA-344 inhibited a reduction in the skin histamine content caused by the 72-hr PCA, without effect on the compound 48/80-induced histamine reduction. AA-344 also partially inhibited the IgGa-mediated 3-hr PCA in rats. These results indicate that the inhibitory action of AA-344 on the immediate hypersensitivity reactions is due to prevention of the release of chemical mediators from the mast cells, by acting on some process in sequential events leading to the mediator release following antigen-antibody combination.

5-Acetylspiro [benzofuran-2 (3H), 1'-cyclopropan]-3-one (1a) shows potent gastric antisecretory and antiulcer activities in rats. In an attempt to improve the pharmacological profile of 1a, we synthesized positional isomers, as well as the prenyloxy and oxime derivatives. Evaluation of their antisecretory activities and protective activities against gastric lesions induced by water-immersion restraint stress in the rat indicated that the 7-acetyl derivative (1d) was equipotent to 1a.

AA-344, which has been evidenced to inhibit selectively IgE-mediated allergic reactions, exhibited an inhibitory effect on cyclic AMP phosphodiesterase (PDase) in the homogenates of purified rat peritoneal mast cells (RMC). AA-344 showed synergistic effects with epinephrine, isoproterenol or prostaglandin E2 and F2α in increasing cyclic AMP level in RMC: the combinations caused an increase in cyclic AMP 30–160 times as much as that caused by the respective agent alone. In the latter effect, AA-344 was at least 1,000 times as potent as theophylline. On the other hand, histamine or serotonin with or without AA-344 had no effect on the RMC cyclic AMP. These results obtained in vitro suggest that AA-344 may exert antiallergic action by increasing cyclic AMP via an interaction with epinephrine or prostaglandins which might be endogenously involved in regulation of a function of RMC in allergic reactions.

Amoxanox inhibited immunologically stimulated and LTD4-induced bronchoconstriction in laboratory animals. Amoxanox, like DSCG, inhibited rat IgE-mediated PCA and histamine release from rat peritoneal mast cells, and suppressed immunologically stimulated or calcium ionophore A23187-induced SRS-A generation in rat peritoneal cavity and guinea pig lung fragments. This compound also reduced the contractile response of guinea pig lung parenchymal and ileal strips to LTD4, but did not significantly affect the response of the ileum to either histamine or acetylcholine. Therefore, the antiallergic action of amoxanox seems to be associated with inhibition of chemical mediator release and antagonistic activity on SRS-A.

Spiro [benzofuran-2 (3H), 1'-cyclopropan]-3-one (VI-1) and its derivatives (VI-2-VI-75) were synthesized in the same manner as described previously for the synthesis of spiro [cyclopropane-1, 2'-[2H] indol]-3'(1'H)-ones (I). These spiro [benzofuran-2 (3H), 1'-cyclopropan]-3-ones were evaluated for gastric antisecretory activity and protective activity against lesions induced by water-immersion restraint stress in the rat. The most potent antiulcer compounds (VI-17 and VI-55) were obtained by the introduction of an acetyl or dimethylamino group at the 5-position on the benzene ring. The most interesting member of the series, 5-acetylspiro [benzofuran-2 (3H), 1'-cyclopropan]-3-one (VI-17, AG-629), was selected as a candidate for clinical studies.

1. 1. Administration of theophylline and gastric acid stimulants, such as histamine, tetragastrin and carbachol, increased the adenosine 3′:5′-cyclic monophosphate (cyclic AMP) level 2–3-fold as comparred with the control. 2. 2. N 6 -2′-O- Dibutyryl cyclic AMP (dibutyryl cyclic AMP) stimulated gastric acid secretion and activity of carbonic anhydrase in rat gastric mucosa. 3. 3. In vitro addition of cyclic AMP ( 10 −5 −10 −7 M ) to the supernatant fraction (cytosol) of rat gastric mucosa caused a concentration dependent potentiation of carbonic anhydrase activity. It is considered that this activation was mediated through protein kinase activation.