Effect of melatonin on vascular reactivity in pancreatectomized rats.
The present study was undertaken to assess whether the improvement of contractile performance of aortic rings by melatonin described in streptozotocin diabetic rats also occurs in another model of type I diabetes, the pancreatectomized rats. Adult male Wistar rats submitted to a subtotal pancreatectomy and exhibiting altered levels of fasting glucose and an abnormal tolerance glucose test, were used. Sham-operated laparotomized rats were employed as controls. Dose-response curves for acetylcholine-induced, endothelium-related relaxation of aortic rings (after previous exposure to phenylephrine) and for phenylephrine-induced vasoconstriction were conducted. This protocol was repeated with rings pre-incubated in a high glucose solution (44 mmol/l). Pancreatectomy decreased significantly acetylcholine-induced relaxation of aortic rings, but not phenylephrine-induced vasoconstriction, the effect being amplified by preincubation in high glucose solution. The deleterious effect of a high glucose medium was more pronounced in pancreatectomized rats. Melatonin (10(-5) M) did not modify acetylcholine-induced relaxation in normal glucose concentration but was effective to prevent the impairment of relaxation brought about by exposure to high glucose solution. The contractile response to phenylephrine of aortic rings obtained from pancreatectomized rats was not affected by melatonin. The results further support the improvement by melatonin of endothelial-mediated relaxation in blood vessels of diabetic rats.
Reyes-Toso
Carlos F
CF
Department of Physiology, Faculty of Medicine, University of Buenos, Aires, Paraguay 2155, 1121 Buenos Aires, Argentina.
Linares
Laura M
LM
Ricci
Conrado R
CR
Arán
Martín
M
Pinto
Jorge E
JE
Rodríguez
Ricardo R
RR
Cardinali
Daniel P
DP
D000109:Acetylcholine / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000503:physiopathology*; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D007813:Laparotomy; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D009126:Muscle Relaxation / Q000187:drug effects*; D010180:Pancreatectomy; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D014665:Vasodilator Agents; D010656:Phenylephrine; D005947:Glucose; D008550:Melatonin; D000109:Acetylcholine