AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 3 584-R590, Copyright © 1993 by American Physiological Society

ARTICLES

Role of angiotensin II and prostaglandins in the regulation of uteroplacental blood flow

L. L. Woods
Division of Nephrology and Hypertension, Oregon Health Sciences University, Portland 97201-3098.

This study was designed to determine the importance of the renin-angiotensin (RAS) and prostaglandin (PG) systems in regulating uteroplacental blood flow (UBF). Our objectives were to determine: 1) whether angiotensin II (ANG II) acts as a vasodilator or purely as a vasoconstrictor in the uteroplacental circulation, and 2) whether this circulation is capable of autoregulation. In chronically instrumented pregnant dogs (41-54 days gestation), ANG II was infused intravenously at increasing doses (8, 16, and 24 ng.kg-1 x min-1). Arterial pressure rose from 108 +/- 6 to 146 +/- 4 mmHg and UBF did not change but uterine vascular resistance (UVR) progressively increased. When the experiment was repeated while servo-controlling uterine arterial pressure, UBF fell at all doses, reaching 62 +/- 7% of control at the highest dose, and UVR increased as before. Meclofenamate (6 mg/kg i.v.) did not alter the dose-response curves. In separate experiments, uterine perfusion pressure was reduced in steps to 55 mmHg. UBF was well autoregulated down to approximately 85 mmHg, and neither captopril (14 micrograms.kg-1 x min-1) nor meclofenamate altered UBF autoregulation. Thus ANG II appears to act as a vasoconstrictor in the uteroplacental circulation and any preservation of UBF during ANG II appears to be due to the increased arterial pressure. Also, in the dog the uteroplacental circulation possesses a mild to moderate degree of autoregulatory capability, which does not appear to be dependent on the RAS or PGs.

This article has been cited by other articles:

				C. R. Rosenfeld Mechanisms regulating angiotensin II responsiveness by the uteroplacental circulation Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2001; 281(4): R1025 - R1040. [Abstract] [Full Text] [PDF]

				B. E. Cox, C. E. Williams, and C. R. Rosenfeld Angiotensin II indirectly vasoconstricts the ovine uterine circulation Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2000; 278(2): R337 - R344. [Abstract] [Full Text] [PDF]