Comparison of vasorelaxants in human basilar arteries and umbilical arteries.

The vasodilatation produced by adenosine, sodium nitrite, and papaverine was compared on isolated human basilar arteries and umbilical arteries precontracted with 30 mM KCl or submaximal concentrations of serotonin and prostaglandin F2 alpha. The basilar artery was far more sensitive to the vasodilators than the umbilical vessel. Papaverine, for instance, was 133 times more effective (EC50 = 3.9 x 10(-6) M) in basilar arteries precontracted with KCl than it was in the umbilical artery (EC50 = 5.2 x 10(-4) M) and all dilators inhibited by at least 95% basilar arteries precontracted with serotonin or prostaglandin F2 alpha. In contrast, umbilical arteries precontracted with KCl or prostaglandin F2 alpha failed to relax significantly to adenosine and sodium nitrite at concentrations that exceeded 10(-3) M, and contractions elicited by serotonin were inhibited by less than 40%. The results support the concept that physiological mechanisms responsible for dilation in most vessels are deficient in the umbilical artery and that the deficiency may be related to the role this atypical vessel plays in closure of the extracorporeal circulation at birth.