title: The effect of changes in perfusion pressure on uteroplacental blood flow in the pregnant rabbit.
abstract: The effect of perfusion pressure on uteroplacental blood flow was determined in pregnant rabbits utilizing the radioactive microsphere method. Control mean arterial pressure, 93 mm Hg +/- 2.6 SEM, was raised by carotid ligation to 109 +/- 4.1 mm Hg and then reduced with antihypertensive drugs to 74 +/- 1.3 mm Hg. Over this range of pressure there was no significant change in cardiac output, 605 +/- 36, 523 +/- 37, and 540 +/- 39 ml/min; or uteroplacental blood flow, 30 +/- 3.2, 27 +/- 5.2, and 29 +/- 4.5 ml/min, respectively. When prostaglandin synthesis was inhibited with either indomethacin or meclofenamate (2 mg/kg), uterine vascular resistance was higher but maintenance of uteroplacental flow occurred over a perfusion pressure of 89 +/- 6.7-115 +/- 9.3 mm Hg. With more severe hypotension induced with trimethaphan, control arterial pressure fell from 92 +/- 2.4 to 39 +/- 0.9 mm Hg, cardiac output fell from 514 +/- 17 to 407 +/- 22 ml/min (P less than 0.025) and uteroplacental blood flow fell from 6.1 +/- 0.9 to 2.5 +/- 0.9% of cardiac output (P less than 0.05), which represented an absolute fall from 32.4 +/- 5 to 10.6 +/- 3 ml/min (P less than 0.025). There was no significant change in renal blood flow expressed as percentage of cardiac output, 14.9 +/- 2 and 13 +/- 1.5%, or in absolute flow, 75 +/- 7.7 and 54 +/- 7 ml/min with trimethaphan-induced hypotension. These studies indicate that uteroplacental blood flow is maintained relatively constant over a range of perfusion pressure of 60-140 mm Hg in both normal and prostaglandin-inhibited pregnant rabbits. However, with reduction in pressure to 36-42 mm Hg, uteroplacental blood flow falls, expressed as a percentage of cardiac output and in absolute flow.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D002339:Carotid Arteries / Q000601:surgery; D003864:Depression, Chemical; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D008026:Ligation; D008469:Meclofenamic Acid / Q000494:pharmacology; D008863:Microspheres; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D011458:Prostaglandins E / Q000096:biosynthesis / Q000097:blood / Q000494:pharmacology; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects; D014599:Uterus / Q000098:blood supply*; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D011458:Prostaglandins E; D008469:Meclofenamic Acid