Placental transfer and distribution of toluene, xylene and benzene, and their metabolites during gestation in mice.

The distribution of radioactivity in pregnant mice was registered at different time intervals (0-24 h) after a 10 min period of inhalation of 14C-toluene, -xylene, and -benzene. Autoradiographic and liquid scintillation methods were used to make possible the distinction between volatile, water-soluble and firmly tissue-bound radioactivity. Toluene, xylene, as well as benzene reached high concentrations immediately after inhalation in lipid-rich tissues (brain and fat) and well perfused organs (e.g., liver and kidney) but were rapidly eliminated resulting in low concentrations at 1 h in all maternal tissues, except fat. Metabolites reached peak levels around 30 min to 1 h after inhalation, but were also relatively rapidly eliminated. One exception from this general trend was a retention of firmly tissue-bound metabolites in maternal liver and kidney after benzene inhalation. Another exception was the very strong accumulation of water-soluble metabolites at 4 and 24 h in the nasal mucosa and olfactory bulb after inhalation of toluene and xylene. Volatile radioactivity was observed in the placenta and fetuses immediately and up to 1 h after inhalation of all the three studied solvents at all stages of gestation. The fetal levels were, however, much lower than in maternal tissues. In early gestation an even distribution pattern was observed, while the fetal liver reached higher concentration than other fetal tissues in late gestation. In similarity with maternal tissues, fetal tissues reached the highest levels of metabolites 30 min to 1 h after inhalation. A retention in uterine fluid was seen at 4 h. Otherwise no retention of metabolites was observed in the feto-placental unit.(ABSTRACT TRUNCATED AT 250 WORDS)