Studies on the biosynthesis of cytochrome P-450 in rat liver—A probe with phenobarbital

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

“…This is consistent with the location of this variant on the cytosolic face of the membrane (Bar-Nun et al, 1980). Similar results have been found for phenobarbital-induced cytochromes P-450 (Dubois & Waterman, 1979;Bhat & Padmanaban, 1979;Colbert et al, 1979;Bar-Nun et al, 1980) and for other induced microsomal membrane proteins such as epoxide hydratase (Pickett et al, 1980) and NADPH-cytochrome c (P-450) oxidoreductase (Gonzalez & Kasper, 1980). Our data do not preclude the possible presence of a retained 'signal' peptide sequence on the N-terminus of the 52K P-450 molecule.…”

Turnover of messenger RNA, apoprotein and haem of cytochrome P-450b + e induced by phenobarbitone in rat liver

“…It is now well established that prototype drugs such as phenobarbitone and 3-methylcholanthrene induce specific species of cytochrome P-450 in liver (Lu & West, 1980;Ryan et al, 1982;Yuan et al, 1983). This induction is associated with an increase in specific mRNA (Bhat & Padmanaban, 1979;Adesnik et al, 1981;Morville et al, 1983) and the prototype drugs have been shown to act at the level of transcription (Hardwick et al, 1983; Atchison & Adesnik, 1983). Dubois & Waterman (1979) reported that, whereas the translatable cytochrome P-450 mRNA activity in response to a single injection of phenobarbitone to rats reaches a maximum around 16h, the holoprotein content measured spectrally reaches a maximum around 45 h. In a preliminary study, we had reported that the cytochrome P-450b + e species (inducible by phenobarbitone) in the normal uninduced animal turns over with halflives around 12 h and 5 h for the apoprotein and haem moieties respectively ).…”

“…The specific protein contents were calculated from a standard curve relating known concentrations of purified cytochrome P-450b and the square of the ring diameter. The protocols used for cytochrome P-450b purification from phenobarbitone-treated rats and for isolation and purification of antibodies have been described previously (West et al, 1979;Bhat & Padmanaban, 1979).…”

Effect of phenobarbital on the level of translatable rat liver epoxide hydrolase mRNA.

“…With the recent advances in the purification of multiple species of cytochrome P-450, the development of specific antibodies to these different forms (9-11), and the refinements made in cellfree translation systems, it became possible to examine the molecular basis of induction of cytochrome P-450 by various xenobiotics. As a result, studies from a number of laboratories (12)(13)(14)(15)(16) have demonstrated that the level of functional mRNA for the phenobarbital-inducible species of cytochrome P-450 in rats is increased by 12-16 hr after a single injection of phenobarbital.Despite the recent advances in the purification and characterization of rat liver epoxide hydrolase, only recently have any studies focused on the capacity of mRNA isolated from phenobarbital-treated rats to direct the synthesis of epoxide hydrolase (17, 18). Both of these brief communications reported that the primary translation product of epoxide hydrolase appears to be synthesized in cell-free systems as the mature enzyme.…”

“…With the recent advances in the purification of multiple species of cytochrome P-450, the development of specific antibodies to these different forms (9)(10)(11), and the refinements made in cellfree translation systems, it became possible to examine the molecular basis of induction of cytochrome P-450 by various xenobiotics. As a result, studies from a number of laboratories (12)(13)(14)(15)(16) have demonstrated that the level of functional mRNA for the phenobarbital-inducible species of cytochrome P-450 in rats is increased by 12-16 hr after a single injection of phenobarbital.…”