Determination of Time to Steady-state Level in Blood during Inhalation Exposure of Benzene by Rats and Mice Part 1.

摘要

The benzene uptake rate was evaluated in five male Sprague Dawley rats and twentyfive male Swiss albino mice receiving benzene at a nominal concentration of 300ppm in a dynamic air flow chamber for 6 hours. Five individual rats were determined to have an internal mean benzene uptake rate of 152ml/min prior to conducting the six hour test and an mean pretest respiratory minute volume of 145ml/min. The mean benzene uptake rates as compared to pretest values for rats decreased to 33, 22 and 9% of the mean test value 1, 3 and 6 hours after administration, respectively. The mean minute volume for rats decreased to 85, 78 and 66% of thepretest at 1, 3 and 6 hours after administration, respectively. Rats had an estimated retained dose of 56mg/kg. Mice (5/group) had a mean total pretest benzene uptake rate of 188ml/min and a mean pretest total respiratory minute volume of 189ml/min. The mean total benzene uptake for the mice decreased 65, 76 and 81% of the pretest value, after 1, 3 and 6 hours of exposure, respectively. The mean total minute volume for groups of mice decreased 96, 84 and 69% of the pretest after 1, 3 and 6 hours, respectively. The mean total retained dose per mice was estimated to be 377mg/kg. The concentration of benzene and it's metabolites were determined after 12, 24, 48 and 72 hours in the urine of five exposed male Sprague Dawley rats and 25 male Swiss albino mice which received a nominal concentration of benzene at 300ppm in dynamic air flow chamber for 6 hours. No level of benzene at or above the detection limit (1.0ppm) were detected in rat and mice urine at any of the sampling intervals. The level of free phenol in the rat urine were 2.0, 2.2, 1.7 and 3.2ppm and in mouse urine were 15.6, 4.7, 5.8 and 4.3ppm at 12, 24, 48 and 72 hours, respectively. The mean levels of free catechol in rat urine were < 2.0, 0.46, 0.32 and < 2.0ppm and in mouse urine were 1.09, 1.29, 1.56 and 7.76ppm at 12, 24, 48 and 72 hours, respectively. No free hydroquinone at or above the detection limit were determined in rat urine at any sampling time. The mean levels of free hydroquinone in mouse urine were 12.87, 1.49, 1.46 and 0.31ppm at 12, 24, 48 and 72 hours, respectively. The expired air of rats was bubbled through dichloromethane and the mean total levels of benzene detected were 440.6, 101.4, not detected and 22.2ug/sampling interval ending at 6, 12, 24 and 48 hours, respectively. Benzene in expired air of mice was only detected at the 48 hour sampling interval. Project No. 79-7242 Determination of Material Balance of Benzene in Rats and Mice. Determination of Material Balance of Benzene in Rats and Mice Part Ii.