Biochemical and morphological effects of long-term inhalation exposure of rats to ethylbenzene

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Abstract
1. Male Wistar rats were exposed (six hours/day, five days/week) to 0, 50, 300 or 600 p.p.m. of ethylbenzene vapour in the air, and killed after 2, 5, 9 or 16 weeks of exposure. 2. After 600 p.p.m., liver-microsomal protein but not cytochrome P-450 concn. was slightly increased; NADPH-cytochrome c reductase was increased maximally by 30% (1·3-fold), 7-ethoxycoumarin O-deethylase (1·8-fold) and UDPG-transferase (2·3-fold). The increase in liver-cytosolic D-glucuronolactone dehydrogenase paralleled the glucuronidation activity (≤2-fold). 3. In the kidneys, only 7-ethoxycoumarin O-deethylase (·3·5-fold) and UDPG-transferase (≤1·8-fold) showed dose-related increases. 4. Ethylbenzene exposure did not deplete hepatic glutathione (GSH); kidney GSH was slightly increased (≤1·3-fold) according to dose. 5. Urine excretion of thioethers was increased with dose, and at 600 p.p.m. was eight times control levels. 6. At 600 p.p.m. there was no increase in serum alanine aminotransferase activity, and liver cells showed slight proliferation of smooth endoplasmic reticulum, slight degranulation and splitting of rough endoplasmic reticulum and enlarged mitochrondria, but no necrosis.