Role of the nitric oxide on diazoxide‐induced relaxation of the calf cardiac vein and coronary artery during cooling

The effects of cooling (to 28 degrees C) on the vasodilation induced by diazoxide (10(-9)-3 x 10(-4) M) on carbachol-pre-contracted calf cardiac vein and coronary artery and the role of nitric oxide in these effects were analyzed. Diazoxide produced concentration-dependent relaxation of calf cardiac vein and coronary artery rings pre-contracted with carbachol (10(-6) M). During cooling, the pIC(50) values, but not the maximal responses, to diazoxide were significantly lower than at 37 degrees C in both preparations. Cooling to 28 degrees C in the presence of N(G)-nitro-L-arginine methyl ester (10(-4) M) did not modify the effect of temperature both in cardiac vein and coronary artery. These results suggest that cooling-induced changes of diazoxide in calf cardiac vein and coronary artery are independent of nitric oxide.