title: Maternal estradiol response to alterations in uteroplacental blood flow.
abstract: Low levels of maternal estrogens are commonly regarded as indicators of fetal stress. We continuously monitored distal aortic blood flow by flowmeter, fetal heart rate, and amniotic fluid pressure in seven pregnant baboons near term. Four of the animals received a constant intravenous infusion of [7-3H]dehydroepiandrosterone and [4-14C]estradiol for 270 minutes. A 50% reduction in mean distal aortic blood flow was imposed after 60 minutes by means of partial occlusion of the aorta with a snare device and released at 180 minutes. Blood was collected at 10-minute intervals from 30 to 60 minutes, 120 to 180 minutes, and 240 to 270 minutes. Concentrations of dehydroepiandrosterone, dehydroepiandrosterone sulfate, estradiol, and cortisol in maternal plasma were determined by radioimmunoassay. Metabolic clearance rates of dehydroepiandrosterone and estradiol were calculated from plasma concentrations of [3H]dehydroepiandrosterone and [14C]estradiol. There was no significant change in maternal levels of dehydroepiandrosterone, dehydroepiandrosterone sulfate, or cortisol with alterations in distal aortic blood flow. Three animals exhibited no fetal heart rate evidence of fetal stress; estradiol levels declined during occlusion and returned toward control after release of the snare. Four animals exhibited repetitive late decelerations under conditions of reduced flow; estradiol was unchanged or rose slightly during occlusion but increased three- to 10-fold after release whereas the metabolic clearance rate of both dehydroepiandrosterone and estradiol remained stable. We conclude that placental hypoperfusion without fetal stress results in decreased conversion of aromatizable substrate and elevated maternal estradiol levels during acute hypoxemic fetal stress probably represent increased production of fetal androgen.
mesh_terms: D000818:Animals; D003687:Dehydroepiandrosterone / Q000031:analogs & derivatives / Q000097:blood; D019314:Dehydroepiandrosterone Sulfate; D004958:Estradiol / Q000097:blood*; D005260:Female; D005316:Fetal Distress / Q000503:physiopathology*; D006340:Heart Rate, Fetal; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D010215:Papio; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D012039:Regional Blood Flow; D014599:Uterus / Q000098:blood supply*
chemical_list: D003687:Dehydroepiandrosterone; D004958:Estradiol; D019314:Dehydroepiandrosterone Sulfate; D006854:Hydrocortisone