SEX-DEPENDENT DIFFERENCE IN ETHYLMORPHINE N-DEMETHYLASE IN HEPATIC MICROSOMES OF RATS

The activation energies for the activity of ethylmorphine N-demethylas e under the condition of higher temperature than break point were not different between male and female rats. In contrast, the value under t he condition of lower temperature than break point in female rats was higher than that in male rats. Tn Arrhenius plot analysis, the phase t ransition point for ethylmorphine N-demethylase and aniline p-hydroxyl ase was not different in male and female rats. From these results it s eems likely that the difference in the distribution of P-450 involved in the ethylmorphine N-demethylation might play, in part, an important role in the appearance of the sex-dependent difference in the activit y of ethylmorphine N-demethylation other than the differential express ion of the sex-specific P-450 enzyme(s) such as the P-450 3A subfamily acting as ethylmorphine N-demethylase in rat liver microsomes.