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The role of melatonin and L‐tryptophan in prevention of acute gastric lesions induced by stress, ethanol, ischemia, and aspirin
Author(s) -
Brzozowski Tomasz,
Konturek Peter Ch.,
Konturek Stanislaw J.,
Pajdo Robert,
Bielanski Wladyslaw,
Brzozowska Iwona,
Stachura Jerzy,
Hahn Eckhart G.
Publication year - 1997
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1997.tb00339.x
Subject(s) - melatonin , aspirin , tryptophan , medicine , endocrinology , ischemia , radioimmunoassay , chemistry , gastric mucosa , pineal gland , stomach , biochemistry , amino acid
Brzozowski T, Konturek PCh, Konturek SJ, Pajdo R, Bielanski W, Brzozowska I, Stachura J, Hahn EG. The role of melatonin and L‐tryptophan in prevention of acute gastric lesions induced by stress, ethanol, ischemia, and aspirin. J. Pineal Res. 1997; 23:79–89. ©Munksgaard, Copenhagen Abstract Melatonin, a pineal hormone, synthesized from L‐tryptophan, is known to exist in the gut and to scavenge oxygen free radicals but its role in gastroprotection against acute lesions induced by various strong irritants has been little studied. In this study, we determined the effects of melatonin and L‐tryptophan on gastric secretion and the formation of acute gastric lesions induced by absolute ethanol, acidified aspirin (ASA), stress, and ischemia‐reperfusion (I/R). Area of gastric lesions was determined by planimetry, gastric blood flow (GBF) was measured using a H 2 ‐gas clearance technique, and blood was withdrawn for the measurement of free radicals, plasma gastrin, and melatonin concentration by specific radioimmunoassay. Intragastric (ig) administration of melatonin (2.5–10 mg/kg) or L‐tryptophan (25–200 mg/kg) failed to affect gastric lesions by ethanol and ASA but dose‐dependently reduced the lesions provoked by stress and I/R; this protective effect was accompanied by a significant rise in plasma melatonin level, GBF, and DNA synthesis and by a marked fall in blood free radicals. L‐tryptophan, which significantly elevated the plasma melatonin by about 3–5‐fold, also reduced the stress and I/R‐induced lesions and blood levels of free radicals, while increasing the GBF, DNA synthesis, and plasma gastrin levels. Inhibition of mucosal generation of PGE 2 by indomethacin abolished the protection and the rise of GBF afforded by melatonin and L‐tryptophan, whereas pretreatment with N G ‐nitro‐L‐arginine (L‐NNA), to suppress nitric oxide (NO) synthase, was without any effect. We conclude that melatonin applied exogenously in pharmacological doses and that released by the administration of its precursor, L‐tryptophan, protect gastric mucosa from the damage induced by stress and I/R possibly by a mechanism involving the scavenging of free radicals and gastric hyperemia probably mediated by endogenous prostaglandin but not NO.