UNIQUE BEHAVIOR OF BENZENE MONO-OXYGENASE - ACTIVATION BY DETERGENT AND DIFFERENT PROPERTIES OF BENZENE-INDUCED AND PHENOBARBITAL-INDUCED MONO-OXYGENASE ACTIVITIES

The benzene mono-oxygenase present in liver microsomes from untreated rats was activated 3.5-fold by the detergent Renex 690. This is the first report of an activation of a microsomal mono-oxygenase by detergent. Metyrapone also activated benzene mono-oxygenase, albeit not as strongly (1.5-fold). Treatment of the rats with benzene or phenobarbital induced the benzene mono-oxygenase activity about 3-fold. The benzene-induced form was also activated by the detergent and by metyrapone. However, the phenobarbital-induced activity was inhibited by both modulators. When the mono-oxygenase activity was measured with 7-ethoxycoumarin as a model substrate, which is accepted by many microsomal mono-oxygenases, the phenobarbital-induced activity was inhibited strongly (∼ 80 per cent) by metyrapone or Renex 690; however, both the benzene-induced and the control activity were inhibited only weakly (∼ 30 per cent). The results provide evidence for substantially different properties of the phenobarbital-induced mono-oxygenase(s) compared to control mono-oxygenase(s). Moreover, benzene appears to be a type of inducer different from the known types and of special interest since, whether assayed with benzene or 7-ethoxycoumarin as substrates, and Renex 690 or metyrapone as modulators, the benzene-induced mono-oxygenase activity possesses characteristics resembling the controls rather than that induced by phenobarbital. © 1979.