title: Immunochemical evidences that hexachlorobenzene induces two forms of cytochrome P-450 in the rat liver microsomes.
abstract: Induction by hexachlorobenzene (HCB) of the liver microsomal system of metabolism of xenobiotics has been studied in comparison with the inductions by phenobarbital (PB) and 3-methylcholanthrene (MC). It has been shown that HCB increases the content of cytochrome P-450 in the microsomes. Like PB, HCB induces the activities of aminopyrine- and benzphetamine-N-demethylases. At the same time HCB increases also the activities of benzpyrenehydroxylase and 7-ethoxyresorufin-O-deethylase, which are characteristic of the MC-induction. However, sodium dodecyl sulphate (SDS)-electrophoresis on polyacrylamide gel has revealed that HCB, similar to PB, induces protein with Mr = 52 000 (cytochrome P-450), but not the protein with Mr = 56 000, which is the main isoenzyme of cytochrome P-450 in MC-microsomes (P-448). Using specific antibodies to isolated cytochromes P-450 and P-448 (anti-P-450 and anti-P-448) it has been found by rocket immunoelectrophoresis that in HCB-treated microsomes 20% of the total cytochrome P-450 consist of PB-form and about 10% comprise cytochrome P-488. It has also been found that anti-P-448 totally inhibit 7-ethoxyresorufin-O-deethylase activity of HCB-microsomes while anti-P-450 was inactive. The data presented give direct proof that HCB exemplifies an individual chemical compound which is able to initiate the synthesis of both PB-form and MC-form of the cytochrome P-450.
mesh_terms: D000818:Animals; D002722:Chlorobenzenes / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction; D006581:Hexachlorobenzene / Q000494:pharmacology*; D005779:Immunodiffusion; D007122:Immunoelectrophoresis; D007527:Isoenzymes / Q000096:biosynthesis / Q000302:isolation & purification; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000378:metabolism*; D008970:Molecular Weight; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002722:Chlorobenzenes; D007527:Isoenzymes; D006581:Hexachlorobenzene; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D010634:Phenobarbital