Induction by phenobarbital of the mRNA for a specific variant of rat liver microsomal cytochrome P-450

Abstract

The treatment of rats for 4 days with phenobarbital causes an apparent 3-fold increase in the amount of total liver cytochrome P-450. By sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, metyrapone binding and immunoprecipitation, this increase was found to be due to a much larger increase in a restricted number of specific cytochrome P-450 variants. A radioimmunoassay technique demonstrated that the major phenobarbital-inducible variant, of molecular weight 52 000, is induced 24-fold by phenobarbital. Immunoprecipitation analysis of products of translation in vitro with an antibody specific to the 52 000-mol.wt. cytochrome P-450 showed that phenobarbital induces the mRNA in polyribosomes for this variant 20-fold. Evidence is presented for the action of phenobarbital at the transcriptional and translational levels.

Phenobarbital induction of cytochrome P-450 gene expression

“…The induction of P-450 2B by PB is primarily due to new 2B protein synthesis that results from an increase in steady state levels of 2B mRNA (Adesnik et al, 1981;Phillips et al, 1981). Thus, PB induction of these P-450s apparently does not involve the mRNA stabilization mechanism associated with induction of P-450 1A2 by 3-methylcholanthrene (Kimura et al, 1986;Silver & Krauter, 1988), nor does it involve protein stabilization, which contributes to the induction of 3A P-450(s) by macrolide antibiotics (Watkins et al, 1986) and the induction of P-450 2E1 by acetone (Song et al, 1989) (Table 3).…”

Deletion of the mouse Fmo1 gene results in enhanced pharmacological behavioural responses to imipramine

“…Microsomal membrane vesicles were isolated from the liver of male (n = 3) or female (n = 3) wild-type or knockout mice as described earlier [31]. Microsomal vesicles from Spodoptera frugiperda (Sf) 9 cells expressing either human FMO1 or FMO3 were isolated as described earlier [33].…”

“…Microsomal membrane vesicles were isolated from the male (n = 3) and female (n = 3) mouse tissues as described earlier [31]. Western blotting was performed as described earlier [32].…”

Species Differences in Cytochromes P450 and Their Corresponding Messenger Rna's

“…Various groups have shown that PB administration results in an increase in the mRNA coding for cytochrome P-450 b (90,91), and Phillips, et al (90) have estimated that there is approximately an 18 fold increase of 52 Κ cytochrome P-450 mRNA in the livers of Sprague Dawley rats. However following PB administration, it has been observed that the increase of spectrophotometrically detectable cytochrome P-450 reaches a maximum at about 45 hours after a single injection of phenobarbital whilst the increase in cell free translation of apo-cytochrome P-450 directed by the corresponding mRNA, reaches a maximum at 16 hours following PB administration (89).…”

“…PB and 3MC pretreatment of experimental animals results in a 2-3 fold increase in the liver microsomal content of cytochrome P-450 (26,90), and immunological measurements indicate that pretreatment with either xenobiotic inducer leads to a 24-50 fold increase in the levels of different molecular forms of cytochrome P-450, each of which is present at low levels in the liver of uninduced animals (25,26,90). PB treatment for four days was shown to result in a large increase in liver weight (55%) and although the level of polyribosomal RNA per gram of liver increased only slightly (12%), there was a marked enhancement of poly (A) + mRNA in the liver microsomal fraction (82).…”