Effects of cooling and warming on 5-hydroxytryptamine- and acetylcholine-induced contractions of human umbilical vessels: role of nitric oxide

The effects of cooling (to 28 degrees C) and warming (to 41 degrees C) on the vasoconstrictions induced by 5-hydroxytryptamine (5-HT) and acetylcholine (ACh) and the role of nitric oxide in these effects were analyzed in human umbilical artery and vein. 5-HT (10(-9)-10(-4) M) and ACh (10(-9)-10(-4) M) induced concentration-dependent contractions at 37, 28 and 41 degrees C. During cooling, the sensitivity, but not the maximal response, of 5-HT and ACh was significantly higher than at 37 degrees C; and during warming, again the sensitivity, but not the maximal response, of both contractile agents was significantly lower than at 37 degrees C. Neither cooling to 28 degrees C nor warming to 41 degrees C, after treatment with N(G)-nitro-L-arginine methyl esther (L-NAME, 10(-4) M), modify the effect of temperature in both vessels. These results suggest that cooling- and warming-induced responses in human umbilical artery and vein are independent of nitric oxide.