The effect of the inhibition of prostaglandin synthesis on renal blood flow in fetal sheep.

Treatment with prostaglandin synthesis inhibitors has been associated with oligohydramnios in the fetus. The presumed mechanism is a reduction in fetal renal blood flow. We examined the effect of meclofenamate administration on renal blood flow in chronically catheterized fetal sheep during normoxia and during moderate and severe hypoxia. Ten fetal sheep were made hypoxic twice at least 4 days after surgery: once in the presence and once in the absence of meclofenamate infusion. Renal blood flow and combined ventricular output were measured with radioactive microspheres. Prostaglandin synthesis blockade with meclofenamate caused no significant change in blood pressure, combined ventricular output, renal blood flow, or renal vascular resistance in either the normoxic or hypoxic animals. These data challenge the contention that prostaglandin activity protects the renal vascular bed of the fetus from vasoconstriction during hypoxia and they also do not support the hypothesis that prostaglandin synthesis inhibition causes oligohydramnios through reduction of fetal renal blood flow.