Transplacental passage of isoniazid (INH) and its interaction with fetal tissues of mice.

When INH was administered orally or intraperitoneally to pregnant female mice, the concentrations of acetyl INH and acetyl hydrazines did not vary significantly in circulating blood and in amniotic fluid. However, the concentration of INH in the amniotic fluid was significantly higher than that observed in the serum. Autoradiographic studies using 14C-labelled INH revealed that INH crosses the placental barrier and grains can be observed in lung and liver tissues of the fetus. Studies on interaction of 14C-labelled INH with nucleic acids clearly demonstrated that significant amounts of radioactivity were present in all the macromolecules of the whole embryo as well as in those isolated from fetal lung and liver tissues.