[3H]-Salbutamol placental transfer in pregnant rats on the 19th day of gestation.

[3H]-salbutamol added in tracer doses (approximately equal to 250 nmol per animal) to the carrier solution (20 mg/kg) was injected intraperitoneally to pregnant rats on the 19th day of gestation. Some experiments were performed with intravenous administration (approximately equal to 2.5 microCi in 300 microliters 9 g/l NaCl). Drug distribution was studied in the maternal and fetal plasma, lung and liver, and in the placenta and amniotic fluid. 10% of the maternal salbutamol plasma radioactivity was recovered in the fetal plasma, in accordance with earlier findings reported from our laboratory using human placental lobules in vitro.