Effect of propranolol on alpha-amino-isobutyric acid and water kinetics in the materno-fetal unit of the rat.

Pregnant Sherman rats were given propranolol (a) per os (50 mg X kg-1, twice a day) on days 17-19 of gestation, (b) by constant rate infusion: osmotic minipumps (6 mg X kg-1 X day-1) from day 13 of gestation. On day 20 (a-treated) or 21 (b-treated), [14C]-AIB + [3H]-H2O were injected intravenously; plasma and tissue samples were collected at different times up to 4 h (a-treated) or at 2 h (b-treated) for radioactivity measurements. Whatever the treatment, no difference was found between control and treated animals for all parameters studied (number of fetuses; weight, protein; DNA; [14C]-AIB or [3H]-H2O tissue levels) except in propranolol-treated mothers where maternal heart [14C]-AIB uptake was decreased and where fetal plasma and tissue [3H]-H2O levels where higher than control at 5 min. Another set of experiments were performed in a-treated rats. On day 20, each mother was anesthetized with ether and injected as above; maternal plasma sample and one feto-placental unit were collected at different times within 15 min after injection. For this period, [14C]-AIB uptake and mainly [3H]-H2O diffusion were increased in placentae and fetuses of propranolol-treated dams. Arterial blood pressure did not change throughout the experiment in propranolol-treated animals, but decreased in controls. Heart rate was slowed down in the former compared to controls. Thus, in our experimental conditions, propranolol treatment: does not modify fetal weight; has no effect on AIB placental transfer and tissue uptake, and could protect towards the stress of anesthesia and surgical injuries, since H2O transfer was impaired in control but not in treated animals.