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Melatonin restores endothelium‐dependent relaxation in aortic rings of pancreatectomized rats
Author(s) -
ReyesToso Carlos F.,
Linares Laura M.,
Ricci Conrado R.,
ObayaNaredo Daniel,
Pinto Jorge E.,
Rodríguez Ricardo R.,
Cardinali Daniel P.
Publication year - 2005
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.2005.00262.x
Subject(s) - sodium nitroprusside , melatonin , endocrinology , medicine , endothelium , nitric oxide , acetylcholine , aorta , chemistry , endothelial dysfunction , vasodilation , nitric oxide synthase
In rats turned hyperglycemic by a subtotal pancreatectomy, a decreased relaxation response of aortic rings to acetylcholine (ACh) was found; this effect was amplified by preincubation in a high glucose medium (44 mmol/L). The relaxation response to ACh did not occur in endothelium‐denuded rings or after the aortic rings were exposed to l ‐nitro‐arginine methyl ester [ l ‐NAME, a nitric oxide (NO) synthase inhibitor]. Incubation with the NO donor sodium nitroprusside (SNP) restored the impaired relaxation response seen in endothelium‐denuded or l ‐NAME‐treated aortic rings. Pancreatectomy decreased the vasorelaxation of aortic rings caused by SNP. Only in pancreatectomized rats, incubation in a high glucose medium impaired the relaxation effect of SNP. To assess whether melatonin preincubation reversed the impaired relaxation response to ACh (intact endothelium aortic rings) or to SNP (endothelium‐denuded or l ‐NAME‐treated rings) in hyperglycemic rats, cumulative dose–response curves were performed in the presence of 10 −5 mol/L melatonin. Melatonin preincubation did not modify ACh‐induced relaxation of aortic rings in a normal glucose concentration but was highly effective in preventing the impairment of relaxation caused by a high glucose solution. Melatonin was also effective in restoring the impaired SNP‐induced vasorelaxation seen in endothelium‐denuded or l ‐NAME‐treated aortic rings from hyperglycemic rats. The results further support the improvement by melatonin of the endothelial‐mediated relaxation in blood vessels of diabetic rats.