Role of the Nitric Oxide on Relaxation of the Human Umbilical Artery during Cooling

Abstract

In the present study, the effects of cooling (to 28 degrees C) on the vasodilatation induced by diazoxide (10(-9)-3x 10(-4) M), isoproterenol (10(-9)-3x 10(-4) M) and magnesium sulphate (0.1-30 mM) on serotonin-pre-contracted human umbilical artery and the role of nitric oxide in these effects were analyzed. Diazoxide, isoproterenol and magnesium produced concentration-dependent relaxation of human umbilical artery precontracted with serotonin (10(-6) M). During cooling, the pIC(50) values and maximal responses to these agents were significantly lower than at 37 degrees C. Cooling to 28 degrees C in the presence of N-G-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) did not modify the effects of temperature on diazoxide, isoproterenol and magnesium-induced relaxations. These results suggest that cooling-induced changes of diazoxide, isoproterenol, and magnesium sulphate in human umbilical artery are independent of nitric oxide.