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°C) on the vasodilatation induced by diazoxide (10 -9 - 3×10 -4 M), isoproterenol (10 -9 - 3×10 -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°C. Cooling to 28 °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 dia- zoxide, isoproterenol, and magnesium sulphate in human umbilical artery are independent of nitric oxide. © 2011 The Pharmaceutical Society of Japan.