Altered response in vitro of the human umbilical artery to sera of neonates with respiratory distress syndrome and other hypoxic conditions.

A study was made of the reaction of the human umbilical artery and the isolated rabbit auricular artery to protein-free ultrafiltrates of normal and hypoxic sera originating from neonates suffering from RDS or other acute metabolic disturbances. While a normal serum ultrafiltrate caused an enhanced contraction of the umbilical artery, hypoxic sera exerted a weaker pressor activity. At the same time, on the rabbit's isolated auricular artery the hypoxic sera exhibited a higher pressor activity. The phenomenon is in agreement with the clinical observation that spontaneous closure of the umbilical vessels is delayed in the case of fetal hypoxia.