RT Journal Article SR Electronic T1 Effect of phenobarbital treatment and cytochrome P-450 inhibitors on the laurate omega- and (omega - 1)-hydroxylase activities of rat liver microsomes. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 147 OP 151 DO 10.1124/dmd.8.3.147 VO 8 IS 3 A1 R T Okita A1 B S Masters YR 1980 UL http://dmd.aspetjournals.org/content/8/3/147.abstract AB The omega- and (omega - 1)-hydroxylase activities for lauric acid were investigated in rat liver microsomes. Treatment of rats with phenobarbital selectively induced the hydroxylation of the fatty acid (omega - 1)-hydroxylase activity two- to threefold, but had little effect on the omega-hydroxylation reaction. SKF 525-A, metyrapone, and alpha-naphthoflavone inhibited (omega - 1)-hydroxylation, but had only neglible effects on omega-hydroxylation. Metyrapone at 10(-4) inhibited the specific activity of (omega - 1)-hydroxylase 70% in phenobarbital-pretreated rats, but produced only a 10% inhibition of the omega-hydroxylation activity. alpha-Naphthoflavone at 10(-4)M inhibited (omega - 1)-hydroxylase activity 60% in untreated and beta-haphthoflavone-pretreated rats, while omega-hydroxylase activity was decreased only 20%. A selective effect was also observed when microsomes were stored overnight at 4 degrees C. Declines of 50% and 70% were observed in the (omega - 1)-hydroxylase activities after 24 and 48 hr, respectively, whereas omega-hydroxylation decreased only 10-20%. The differential effects on omega- and (omega - 1)-hydroxylase activities of a variety of conditions suggest that distinct cytochromes P-450 mediate the two fattty acid hydroxylases in liver microsomes.