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Circadian rhythm of melatonin and prostaglandin in modulation of stress‐induced gastric mucosal lesions in rats
Author(s) -
Kato K.,
Murai I.,
Asai S.,
Takahashi Y.,
Nagata T.,
Komuro S.,
Mizuno S.,
Iwasaki A.,
Ishikawa K.,
Arakawa Y.
Publication year - 2002
Publication title -
alimentary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.308
H-Index - 177
eISSN - 1365-2036
pISSN - 0269-2813
DOI - 10.1046/j.1365-2036.16.s2.11.x
Subject(s) - melatonin , circadian rhythm , medicine , endocrinology , prostaglandin e2 , prostaglandin , endogeny , nocturnal , gastric mucosa , cyclooxygenase , biology , stomach , enzyme , biochemistry
Background: We previously demonstrated the circadian variation of water‐immersion restraint stress (WRS)‐induced gastric mucosal lesions in rats. Aim: To investigate the roles of melatonin and prostaglandin in the gastric mucosa in circadian modulation of WRS. Methods: Fasted rats were subjected to 4‐h WRS during both the diurnal and nocturnal phases of a light/dark cycle. Mucosal lesions, serum melatonin concentrations, mucosal generation of prostaglandin E 2 (PGE 2 ) and mucosal gene expressions of cyclooxygenase (COX)‐1 and ‐2 were evaluated. Results: Lesion area after 4‐h stress during the dark phase was significantly smaller than that in light‐phase controls. Serum melatonin concentration in control rats during the light phase was significantly increased 4 h after WRS, but PGE 2 generation was decreased by 48% as compared to that in intact mucosa before stress. In the dark phase, melatonin concentration after 4‐h WRS was significantly depressed as compared with the control level at the corresponding time. PGE 2 concentrations after 4‐h WRS in the dark phase were not decreased compared with the control level at the corresponding time, although PGE 2 level was significantly lower than that in light‐phase controls. Expression of COX‐1 and COX‐2 mRNA was detected after exposure to stress in both the light and dark phases. Conclusion: These results suggest that circadian rhythm has an important role in the formation of stress‐induced gastric mucosal lesions in rats. The circadian rhythm of melatonin responses and PGE 2 generation may contribute to nocturnal/diurnal rhythmicity of gastric mucosal defences between day and night.