EFFECTS OF CHRONIC PROPRANOLOL ADMINISTRATION ON THE FETAL AND NEWBORN RAT

Abstract

Normal cardiac β-odrenergic function is important for maintenance of an intact stress response in the fetus and neonate,, Propranolol (P), a β-adrebergic blacker is used to treat hypertension, arrhythmias and thyrotoxicosis in pregnancy and appears to cross the placenta. To determine the effects of daily oral P administration on perinatal mortality and growth and cardiac β-receptor function in the fetus and neonate, we administered P in a graded dosage schedule (5-20 mg/kg/day) to 20 Wistar rats on days 7-22 of pregnancy; 19 rats served as controls. 6 (3 controls) were delivered by caesarean section on day 22 for fetal studies. Neonates were studied at 0-12, 24-36, 48-60 hours postpartum. There were no differences (p>0.05) between P and control rats in maternal weight gain, litter size, number of resorption sites and stillbirths, and pup size and heart weight. Cardiac β-receptor function was studied by recording spontaneous rates of impulse initiation of isolated right atrial strips during control superfusion with Tyrode's solution and following superfusion with epinephrine (E), 1 × 10−5M. E induced a significant rate increase in atria from the controls (p<.01). No rate change (P>.05) was seen in atria from fetuses of P-treated mothers. As age increased to 60 hours postpartum the response to E of P-treated neonates increased. By 48-60 hours this did not differ significantly from control .Hence chronic P administration significantly depresses β-responsiveness of fetal & newborn rat hearts which could be potentially dangerous to the fetus in his adaptation to the stresses of labor.