Mixed type hepatic microsomal enzyme induction by hexachlorobenzene

A comparison of microsomal spectral changes induced by 3-methylcholanthrene, phenobarbitone and hexachlorobenzene has been recorded. In addition, changes after hexachlorobenze treatment of microsomal haem turnover in ‘CO-binding particles’ have been made. Hexachlorobenzene, like 3-methylcholanthrene, alters the spectral characteristics of cytochrome P-450 by shifting its peak to 448 nm. Administration of 5-amino[4- 14C]laevulinate to untreated and hexachlorobenzene-treated rats leads to the incorporation of radioactivity into the haemoprotein(s) of the CO-binding particles obtained from liver microsomes. There is a biphasic loss of radioactivity from the CO-binding particles in both normal and hexachlorobenzene-treated rats. Half-life determinations show that hexachlorobenzene increases the half-life of the fast phase component but not the slow phase component. As a result of these and previous studies, it is proposed that hexachlorobenzene is representative of a new class of inducers which shares the properties of both the polycyclic hydrocarbon group and the phenobarbitone, chlordane group.