Distribution and elimination of 14C-xylene in rat.

Male rats were exposed to about 45 ppm of radioactively labeled xylene in the inspired air for 1--8 h. The distribution and elimination of xylene and metabolites in different organs and tissues were studied. To get an idea of the ratio between unmetabolized and metabolized xylene in organs and tissues, a supplementary study was performed in which five male rats were exposed to about 250 ppm of radioactively labeled xylene. The concentration of xylene and metabolites in the subcutaneous fat, where the largest amounts were found, displayed a sharp rise during the first 4 h of exposure in comparison with the following 4 h. Both during exposure and the decay phase the concentration of xylene and its metabolites in the cerebrum, cerebellum and muscles paralleled the arterial blood concentration and amounted to about 40% of the arterial blood value for xylene. The coefficient between the concentration of unmetabolized xylene in subcutaneous fat and inspiratory air was calculated to be 525 after 8 h of exposure.