Nicotine- or epinephrine-induced uteroplacental vasoconstriction and fetal growth in the rat

We examined the relationship between nicotine-induced vasoconstriction in pregnant rat dams and fetal growth during the third trimester of pregnancy. Pregnant rats were continuously treated between days 13 and 19 of gestation with either nicotine (9.6, 4.8 or 2.4 mg/kg/day), epinephrine (0.72 microgram/kg/day), or saline via continuous infusion from a subcutaneously implanted osmotic minipump. Placental weights in rats treated with high dose nicotine and dams' body weights were severely reduced. However, fetal weights were not affected. Blood flows in uterus and placenta were quantified by measurement of tissue content of 85Sr-labelled microspheres injected via a carotid artery catheter. Both nicotine and epinephrine caused a significant reduction (> 40%) in uterine and placental blood flow. We conclude that vasoconstriction alone as a result of nicotine or epinephrine administration during the last trimester of gestation does not necessarily reduce nutrient supply to the fetus and does not affect fetal growth in rats.