PT  - JOURNAL ARTICLE
AU  - E S Roberts
AU  - A D Vaz
AU  - M J Coon
TI  - Role of isozymes of rabbit microsomal cytochrome P-450 in the metabolism of retinoic acid, retinol, and retinal.
DP  - 1992 Feb 01
TA  - Molecular Pharmacology
PG  - 427--433
VI  - 41
IP  - 2
4099  - http://molpharm.aspetjournals.org/content/41/2/427.short
4100  - http://molpharm.aspetjournals.org/content/41/2/427.full
SO  - Mol Pharmacol1992 Feb 01; 41
AB  - The metabolism of retinoic acid, retinol, and retinal has been investigated with eight purified rabbit cytochrome P-450 (P-450) isozymes, including the major forms in nasal and liver microsomes. Retinoids hydroxylated at the 4-position were found to be major metabolites with each of the isozymes examined. Only two of the isozymes, polycyclic aromatic hydrocarbon-inducible P-450 1A2 and antibiotic-inducible P-450 3A6, also catalyze the oxidation of retinal to retinoic acid, a reaction not previously attributed to P-450. P-450 1A2 showed high activities in both the 4-hydroxylation and aldehyde oxidation reactions. Phenobarbital-inducible P-450 2B4 also had high activity in the 4-hydroxylation reaction of retinoids, and cytochrome b5 was found to increase the activity of P-450 2B4 with each substrate but to increase the activity of P-450 1A2 only with retinoic acid. In microsomes, retinoic acid is converted in an NADPH-dependent manner to both 4-hydroxyretinoic acid and 4-oxoretinoic acid, but none of the isozymes investigated was found to convert the 4-hydroxy derivative to the 4-oxo derivative. Microsomes from animals treated with phenobarbital were more active than those from untreated animals in the 4-hydroxylation reaction and, consequently, showed an increase in the ratio of 4-hydroxy to 4-oxo derivatives produced. These results show that the individual forms of P-450 metabolize retinoic acid, retinol, and retinal to multiple products, and they indicate that the amounts formed may be dependent on the exposure of animals to various inducers of P-450.