Effect of prenatal propranolol exposure on development of the postnatal rat heart

Maternal propranolol (PRO) treatment has previously been associated with adverse effects on the fetus and neonate. In the present study, pregnant rats were treated with PRO (25 or 50 mg/kg/day s.c.) on gestation days 8-20 to assess its possible effects on the developing heart. Maternal weight gain and pup weight on postnatal day (PND) 1 were reduced in a dose-dependent manner; litter size was unaffected. Pup body weight and heart weight both showed a dose-related decrease at all ages tested (PNDs 5/6, 8/9, 15/16, and 22/23). Since heart protein, but not DNA, was similarly reduced, the decrease seen in heart weight most likely reflects a decrease in cell size instead of cell number. Basal ornithine decarboxylase (ODC), an enzyme associated with growth and development, was unaffected by maternal PRO treatment. Insulin and isoproterenol stimulation of ODC, suggested markers for testing the function of the sympathetic pathway to the heart and of the heart's ODC response system, respectively, also showed no PRO-related response. In conclusion, prenatal PRO exposure resulted in reduced body weight, heart weight, and heart protein, but had little effect on heart DNA or ODC activity. Since PRO treatment also reduced maternal weight gain, the adverse effects seen in the pups may be due to generalized PRO toxicity. The results suggest that when high PRO doses were used clinically, the careful monitoring of maternal weight gain during pregnancy might be useful in predicting adverse fetal effects.