Vascular reactivity in diabetic rats: effect of melatonin

• Published in: Journal of pineal research Vol. 33; no. 2; pp. 81 - 86
• Main Authors: Reyes-Toso, Carlos F., Rosón, María I., Albornoz, Liliana E., Damiano, Pablo F., Linares, Laura M., Cardinali, Daniel P.
• Format: Journal Article
• Language: English
• Published: Oxford UK Munksgaard International Publishers 01.09.2002; Blackwell
• Subjects: Acetylcholine - metabolism; Acetylcholine - pharmacology; Adrenergic alpha-Agonists - pharmacology; Animals; Aorta - drug effects; Associated diseases and complications; Biological and medical sciences; Diabetes Mellitus, Experimental - drug therapy; Diabetes Mellitus, Experimental - physiopathology; Diabetes Mellitus, Type 1 - drug therapy; Diabetes Mellitus, Type 1 - physiopathology; Diabetes. Impaired glucose tolerance; Dose-Response Relationship, Drug; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Endothelium, Vascular - drug effects; Endothelium, Vascular - physiology; In Vitro Techniques; Male; Medical sciences; melatonin; Melatonin - metabolism; Melatonin - pharmacology; mild and severe diabetes; Muscle Relaxation - drug effects; Phenylephrine - pharmacology; Rats; Rats, Wistar; Serotonin - metabolism; Serotonin - pharmacology; streptozotocin; vascular reactivity; Vasoconstriction - drug effects; Endocrinopathy; Immunopathology; Melatonin; Rat; Rodentia; Autoimmune disease; Artery; Vascular disease; Vertebrata; Mammalia; Blood vessel; Animal; Insulin dependent diabetes; Aorta; Complication; Circulatory system; Pineal hormone
• ISSN: 0742-3098; 1600-079X
• DOI: 10.1034/j.1600-079X.2002.01886.x

The aim of the present study was to evaluate the in vitro contractile response of rat aorta in mild and severe type I diabetes and the effect of melatonin on it. Aortic rings were obtained from male Wistar rats injected with streptozotocin 8–12 wks earlier. Rats were divided into three groups: non‐diabetic rats (NDR), mildly diabetic rats (MDR) and severely diabetic rats (SDR). Dose–response curves for acetylcholine‐induced, endothelium‐related relaxation of aortic rings (after previous exposure to phenylephrine) and for serotonin‐induced vasoconstriction were conducted in the presence or absence of 10–5 mol/L melatonin. This protocol was repeated with rings preincubated in a high glucose solution (44 mmol/L). The contractile response to phenylephrine decreased in SDR, an effect counteracted by preincubation with high glucose. Melatonin decreased phenylephrine‐induced vasoconstriction in MDR and counteracted the effect of high glucose in SDR. Acetylcholine‐evoked relaxation decreased significantly after exposure to a high glucose in SDR, this effect being counteracted by melatonin. Serotonin‐induced vasoconstriction decreased in SDR and augmented in MDR, but only after exposure to high glucose. Melatonin reduced the maximal tension of aortic contraction after serotonin in MDR, both under basal conditions and after preincubation in a high glucose solution. The results support the existence of differences in vasomotor responses as a function of the diabetes state and of an improvement of contractile performance in diabetic rats after exposure to melatonin at a pharmacological concentration (in terms of circulating melatonin levels but not necessarily for some other fluids or tissues).