Low-dose infusion of atrial natriuretic peptide in the conscious guinea pig increases blood flow to the placenta of growth-retarded fetuses.

Abstract

Our goal was to investigate the effects of low-dose infusion of atrial natriuretic peptide on maternal placental blood flow of normal-sized and growth-retarded fetuses. Seventeen conscious, chronically catheterized guinea pigs were studied at day 50 of gestation after growth retardation was experimentally induced by unilateral uterine artery ligation at day 34. In 12 experiments atrial natriuretic peptide infusion (15 ng/kg/min) increased blood flow (microsphere technique) to placentas of growth-retarded fetuses by 26% (p less than 0.01) while placental blood flow of normal-sized fetuses remained unchanged. This difference in responsiveness to atrial natriuretic peptide infusion was statistically significant (p less than 0.001). Blood pressure, heart rate, and myoendometrial and renal blood flows were unaffected. Plasma concentrations of immunoreactive atrial natriuretic peptide increased by 64%, indicating that physiologic concentrations were achieved. In five saline solution-treated controls none of the studied parameters changed. Atrial natriuretic peptide in low doses selectively increases blood flow to placentas of growth-retarded fetuses in the conscious guinea pig. Infusion of atrial natriuretic peptide in a dose that results in plasma concentrations within the upper physiologic range may have a therapeutic value in pregnancies complicated by intrauterine growth retardation.