The aim of our study was to explore the tissue distribution of 3,5-dimethylbenzene acid (3,5-DMBA) and its excretion with urine of rats and to evaluate toxicokinetics of mesitylene in blood of rats after single and repeated inhalation exposure to mesitylene vapours.
Experiments were performed on male outbred IMP:WIST rats. The animals were exposed to mesitylene vapours at the target concentration of 25, 100, and 250 ppm in dynamic inhalation chambers for 6 h at single exposure and for 4 weeks (6 h/day for 5day/week) at repeated exposure.
The study revealed in rats, after inhalation exposure to mesitylene, exposure-dependent increases in 3,5-DMBA tissue concentration and urinary excretion as well as enhanced mesitylene concentration in tissues and blood. After termination of exposure, mesitylene was rapidly eliminated from blood of rats. Mesitylene retention reduced in rat lungs after repeated exposure, as compared to a single exposure, was most likely the reason for its lower concentration in lungs and blood. Compared with single exposure, 3,5-DMBA concentration increased in rat lungs after repeated inhalation exposure to mesitylene at 100 and 250 ppm, and in the liver at 250 ppm, which may be associated with the induction of mesitylene-metabolizing enzymes.
Mesitylene metabolism in the lungs of the rats after repeated exposure to its low concentrations probably had a significant impact on the increased urinary excretion of 3,5-DMBA.