Flumecinol, a new inducer of the cytochrome P-450 monooxygenases, was studied in rats as a possible effector of liver microsomal testosterone oxidases. The drug enhanced the total content of liver cytochrome P-450 in immature and adult rats. 2. When total testosterone oxidation activity was compared in liver microsomes of treated and untreated rats, no differences in activities were observed in 60-day-old-rats, but a slight decrease was found in 35-day-old treated rats. 3. Several regio- and stereo-specific hydroxylases were modified by flumecinol administration; in 35-day-old rats only 16 alpha-hydroxylation was induced, whereas in 60-day-old rats a slight increase in 2 alpha-hydroxylation was also observed.
