Venous and hepatic vascular responses to indomethacin and prostaglandin E1 in the fetal lamb.

Evidence is accumulating that prostaglandins affect the tone of the ductus venosus. Therefore prostaglandins might alter the distribution of umbilical venous return between the ductus venosus and liver. We have examined the effect of indomethacin and prostaglandin E1 on the vascular resistance of the umbilical-placental circulation, ductus venosus, and liver in 14 chronically instrumented fetal lambs. We found that indomethacin caused a nearly twofold increase in the vascular resistance of both the ductus venosus and liver. Prostaglandin E1, administered 70 minutes after indomethacin at a dose of 0.41 +/- 0.09 (SEM) micrograms/min per kilogram of fetal weight, decreased umbilical-placental blood flow, increased the vascular resistance of the umbilical arteries and placenta, and reversed the elevation of the vascular resistances of the ductus venosus and liver. Because both indomethacin and prostaglandin E1 affected the resistances of the ductus venosus and liver to the same extent, it is unlikely that prostaglandins of the E series mediate the change in distribution of umbilical venous return between the ductus venosus and liver during fetal stress.