Role of nitric oxide in pathogenesis of gastric mucosal damage induced by compound 48/80 in rats.
We examined the effects of various nitric oxide synthase (NOS) inhibitors on development of gastric lesions induced by compound 48/80 (48/80) in rats and investigated the roles of NO and inducible NOS (iNOS) in inflammatory gastric responses. Animals were given 48/80 (1 mg/kg, i.p.) once daily for 4 days, and the stomachs were examined for lesions 24 h after the final administration. NOS inhibitors such as L-NAME, L-NMMA, aminoguanidine or dexamethasone were administered for 4 days during 48/80 treatment. The repeated administration of 48/80 caused damage in the stomach with severe edema in the submucosa. These lesions induced by 48/80 were dose-dependently prevented by concurrent administration of L-NAME. The protective effect of L-NAME on 48/80-induced gastric lesions was mimicked by L-NMMA, aminoguanidine as well as dexamethasone, and significantly antagonized by co-administration of L-arginine but not by D-arginine. Acid secretion was slightly decreased after 48/80 treatment, but was significantly augmented by the combined administration of L-NAME with 48/80. The mucosal MPO activity, TBA reactants and vascular permeability in the stomach were all increased after 48/80 treatment, but these changes were also significantly mitigated by co-administration of L-NAME. The Ca(2+)-independent NOS activity in the mucosa was increased four times during 48/80 treatment, and this change was also inhibited by dexamethasone. These results suggest that: 1) the repeated administration of 48/80 induced inflammatory gastric lesions in the rat stomach; 2) the pathogenic mechanism of these lesions involves endogenous NO produced by iNOS, in addition to oxyradical formation; and 3) the deleterious role of NO during 48/80 treatment may be accounted for by a cytotoxic action of peroxynitrite, which is formed in the presence of NO and superoxide radicals.
Yasuhiro
T
T
Department of Pharmacology and Experimental Therapeutics, Kyoto Pharmaceutical University, Japan.
Konaka
A
A
Ukawa
H
H
Kato
S
S
Takeuchi
K
K
D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005744:Gastric Acid / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D009195:Peroxidase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013276:Stomach Ulcer / Q000139:chemically induced* / Q000473:pathology*; D003189:p-Methoxy-N-methylphenethylamine
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D003189:p-Methoxy-N-methylphenethylamine; D009195:Peroxidase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat