Effects of captopril on blood pressure, placental blood flow and uterine oxygen consumption in pregnant rabbits.

Uterine renin may regulate uteroplacental blood flow locally through changes in vascular resistance or systemically by supporting arterial blood pressure. Captopril (5 mg/kg) was given i.v. to 14 conscious pregnant rabbits at day 27.5 +/- 0.3 of gestation for the purpose of investigating the effects of angiotensin converting enzyme inhibition on uteroplacental blood flow and oxygen consumption. Control measurements (mean +/- S.E.M.) were compared to measurements made at 1 hr (n = 14) and at 3 to 4 hr (n = 7). Arterial blood pressure decreased from 80 +/- 3 to 66 +/- 3 mm Hg, P less than .01, and then declined further to 56 +/- 4 mm Hg, P less than .01. Cardiac output was unchanged at 1 hr, 799 +/- 79 vs. 705 +/- 61 ml/min, but was decreased to 634 +/- 29 ml/min by 3 to 4 hr, P less than .01. There was no change in renal blood flow from 102 +/- 13 ml/min. Total uterine blood flow decreased from 37 +/- 5 to 29 +/- 5 ml/min, P less than .01, and then to 23 +/- 1 ml/min, P less than .01, whereas placental blood flow decreased from 25 +/- 4 to 19 +/- 3 to 15 +/- 3 ml/min, P less than .01; there was no significant change in myoendometrial flow. Oxygen delivery per uterine horn decreased from 2.4 +/- 0.3 to 1.8 +/- 0.4 to 1.6 +/- 0.2 ml/min, P less than .005. Oxygen consumption per horn decreased from 1.31 +/- 0.14 to 1.05 +/- 0.15 ml/min by 1 hr, P less than .05, and there was no further decrease.(ABSTRACT TRUNCATED AT 250 WORDS)