Effect of cooling on vascular smooth muscle response to endothelin-1 in human and rat veins. 
The plasma level of endothelin-1 is locally increased during cooling but the net vasoconstrictor effect will be dependent on temperature effects on the vascular smooth muscle reactivity in response to the polypeptide.  The aim of this study was to investigate the effect of cooling on the vascular smooth muscle response to endothelin-1 in human and rat veins.  Registration of vascular smooth muscle activity in vitro in vessel preparations from normal subjects.  Laboratory.  PATIENTS AND ANIMALS: Superficial hand veins from 14 patients undergoing hand surgery and external jugular veins from 14 rats.  Effects of endothelin-1, after denudation of the endothelium and during cooling, were compared with controls without these interventions.  At 37 degrees C, endothelin-1 induced a concentration-dependent contraction in the human hand and rat jugular veins.  The sensitivity to endothelin-1 was enhanced in segments without endothelium.  At 37 degrees C, no relaxation in response to endothelin-1 was observed.  Cooling to 10 degrees C did not alter precontraction achieved by endothelin-1 at 37 degrees C in the human hand veins, while it depressed the precontraction in the rat jugular vein.  The effect of cold was reversible.  Removal of the endothelium did not alter the response to cooling.  The maintained reactivity in response to endothelin-1 during cooling of the human vessels suggests that the reported increase in endothelin-1 levels due to local cooling could contribute in the pathophysiology of peripheral vasospasm in humans.