Evidence that 2‐allyl‐2‐isopropylacetamide, phenobarbital and 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine induce the same cytochrome P 450 mRNA in chick embryo liver

• Published in: European journal of biochemistry Vol. 136; no. 2; pp. 327 - 332
• Main Authors: BROOKER, John D., SRIVASTAVA, Gopesh, BORTHWICK, Iain A., MAY, Brian K., ELLIOTT, William H.
• Format: Journal Article
• Language: English
• Published: 01-11-1983
• DOI: 10.1111/j.1432-1033.1983.tb07745.x
• EISSN: 1432-1033
• ISSN: 0014-2956

The induction of cytochrome P
450
in chick embryo liver has been studied using three different porphyrinogenic drugs, 2‐allyl‐2‐isopropylacetamide, 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine and phenobarbital. Pulse‐labelling studies have shown that for each drug the cytochrome P
450
synthesised either
in ovo
or in a wheat germ translation system reacted immunologically with antibody raised against the purified 2‐allyl‐2‐isopropylacetamide‐induced enzyme (
M
r
= 50 000).
To investigate whether this is due to the three drugs inducing the same protein or different proteins with common immunological determinants, nucleic acid hybridization studies have been carried out using a recently characterised 2‐allyl‐2‐isopropylacetamide‐induced cytochrome P
450
cloned cDNA probe [Brooker, J. D. et al. (1982)
Eur. J. Biochem. 129
, 325–333]. It has been shown that the mRNA induced by each drug hybridizes with this probe and all are of similar size. The melting profile of the mRNA · cDNA hybrids indicates that the mRNAs induced by the three drugs have at least 98% homology with the cDNA probe.
Restriction endonuclease digestions of total chick embryo genomal DNA and a chick cytochrome P
450
genomal clone indicates that the cytochrome P
450
gene homologous with the cDNA probe is represented in the genome only once.
These results strongly suggest that the three drugs cause increased levels of the same cytochrome P
450
mRNA, possibly due to enhanced expression of the same gene.
Results are also presented which show that other cytochrome‐P
450
‐inducing drugs, 3‐methylcholanthrene, β‐naphthoflavone or pregnenolone‐16 α‐carbonitrile do not increase the level of the 2‐allyl‐2‐isopropylacetamide‐inducible mRNA but rather reduce it to a level which was lower than that of the untreated controls.