Effects of epinephrine on distribution of blood flow in the pregnant ewe.

Seven pregnant ewes ranging from 85 to 140 days of gestation were infused with systemic doses of epinephrine and uterine arterial flow dose-response curves were determined. With a constant systemic infusion of epinephrine at a mean rate of 0.29 +/- 0.03 mug/Kg.-min., and the radionuclide lebeled microsphere method to measure arterial blood flow, a 38.5 per cent decrease in total uterine arterial blood flow was demonstrated while systemic pressure was unaltered. At this dose the reduction in endometrial blood flow was significantly greater (-58.7 per cent) than that in either the myometrium (-36.9 per cent) or placental cotyledons (-34.5 per cent) (p less than 0.025 and less than 0.005, respectively). There also occurred a decrease in blood flow to the mammary gland and the pancreas, whereas increased in blood flow to the skeletal muscle, adipose tissue, and spleen were documented. It is evident from this study that during the period of ovine pregnancy investigated, the vascular bed of all tissues comprising the pregnant uterus, including the placental cotyledons, are sensitive to the vasoconstrictive effects of epinephrine.