[Placental transfer and distribution of betamethasone 17,21-dipropionate in various regions of the brain of pregnant rats and mice (author's transl)].

As betamethasone 17,21-dipropionate induces adrenal atrophy in rat dams and adrenal hypertrophy in the fetus, we investigated the placental transfer of this compound using autoradiography and liquid scintillation counting in animals in the late stages of pregnancy. In these two species, 3H-betamethasone 17,21-dipropionate and/or its metabolites transferred across the placental barrier into fetal tissues and were distributed at levels lower than detected in the maternal tissues. The rat fetus showed a high uptake of radioactivity in the adrenal cortex. In pregnant rats, the ratios of the radioactivity in the adrenal cortex. In pregnant rats, the ratios of the radioactivity in brain tissues to the plasma in fetuses were much higher than in the dams after the administration of 3H-betamethasone 17,21-dipropionate or 3H-betamethasone. In the dams given 3H-betamethasone 17,21-dipropionate, the accumulation of radioactivity in the hypothalamus and septum was significantly greater than in other regions. The present study suggests that betamethasone 17,21-dipropionate or its metabolites transferred across the placental barrier following administration to the mother rat may produce an adrenal hypertrophy in the fetus and that accumulation of radioactivity in the hypothalamus of the dam may be related to a suppression of the function of hypothalamo-pituitary-adrenal axis.