EFFECTS OF CHRONIC INFUSION OF ANGIOTENSIN-II ON RENIN AND BLOOD-PRESSURE IN THE LATE-GESTATION FETAL SHEEP

OBJECTIVES: Our purpose was to determine whether chronic physiologic e levations in plasma angiotensin II levels decrease plasma renin concen tration, alter the relationship between active renin and prorenin in f etal plasma and kidney, and depress the expression or renal renin mess enger ribonucleic acid in the fetus. STUDY DESIGN: Seventeen chronical ly catheterized ovine fetuses at approximately 130 days' gestation wer e infused with either angiotensin II (48.9 +/- 3.5 ng/kg.min) or vehic le (5% glucose in water) for 72 hours. RESULTS: Mean arterial pressure increased significantly by 1 hour of infusion and continued to increa se throughout the infusion. The plasma active renin concentration was significantly decreased by 1 hour of the infusion, whereas the proreni n concentration was not decreased until 24 hours of the infusion. Afte r 72 hours of angiotensin II infusion the renal tissue prorenin conten t decreased (21.5 +/- 5.1 ng/mg.hr angiotensin I vs 46.4 +/- 6.6 ng/mg .hr angiotensin I in the control animals, p = 0.01), whereas the activ e renin concentration did not change (26.6 +/- 5.1 ng/mg.hr angiotensi n I vs 35.1 +/- 5.4 ng/mg.hr angiotensin I in the control animals, p = 0.28). The renal renin messenger ribonucleic acid expression tended t o be lower in the angiotensin II-treated fetuses (p = 0.10). CONCLUSIO N: Chronic physiologic increases in fetal plasma angiotensin II suppre ss the secretion of active and prorenin and alter the relationship bet ween processing and secretion of renin in the fetal kidney.