Effects of arsenite on hepatic mixed-function oxidase activity in rats

1. Injection of arsenite (As³⁺) to control rats results in losses of total hepatic cytochrome P-450 and significant decreases of ethoxycoumarin O-deethylase (ECOD) and ethoxyresorufin O-deethylase (EROD) activities. However, As³⁺ appears to decrease the activity of these enzymes differentially, with EROD showing greater sensitivity than ECOD.

2. Injection of As³⁺ to rats treated with phenobarbital and isosafrole significantly decreases the total content of hepatic cytochrome P-450 and various mixed function oxidase (MFO) activities, with the exception of ECOD which appears to be insensitive to As³⁺.

3. 3-Methylcholanthrene administration apparently protects against the effects of As³⁺ on the cytochrome P-450 system, since total content of the cytochrome P-450 and various MFO activities were all insensitive to this treatment.