[Effects of chronic exposure of ethylene oxide, especially on heme metabolism]

The changes in the cytochrome P-450 enzyme system of rat liver, lung and brain after inhalation of ethylene oxide were studied. When Wistar male rats were exposed to 500 ppm ethylene oxide three times a week for three months, they showed a suppressed gain of body weight. Therefore, the present study was done using pair-fed rats. Haematological examination revealed normocytic and normochromic anemia. Liver and renal functions were normal. The cytochrome P-450 enzyme system in the lung and brain were not affected. However, hepatic cytochrome P-450 and protoheme decreased by 28% and 19%, respectively. Hepatic total microsomal protein, cytochrome b5, NADPH-cytochrome c reductase and NADH-ferricyanide reductase were not affected. The activity of hepatic heme oxygenase showed a 2-fold increase. These results suggest that the heme moiety of hepatic cytochrome P-450 was primarily attacked by exposure of ethylene oxide and the cellular heme balance in liver was altered.