IN VIVO AND IN VITRO INDUCTION OF ARYL HYDROCARBON HYDROXYLASE IN MAMMALIAN CELLS OF DIFFERENT SPECIES, TISSUES, STRAINS, AND DEVELOPMENTAL AND HORMONAL STATES

Aryl hydrocarbon hydroxylase from rat liver metabolizes a variety of polycyclic hydrocarbons. This membrane-bound enzyme system is present in various tissues of the monkey, hamster, and rat. In vivo, the prior administration of a polycyclic hydrocarbon induces the hydroxylase to higher levels in the liver, lung, gastrointestinal tract, and kidney of each of these mammals. The enzyme is also present in various tissues of six strains of mice; the hepatic enzyme is inducible in the Swiss, strains C-57, C3H, and A, but not in strains AKR/N or DBA, of the mouse. Thus, there are genetic differences in the regulation of enzyme induction as well as in the control levels of enzyme. The enzyme system is also induced transplacentally: treatment of the pregnant hamster or rat, with either a polycyclic hydrocarbon or phenobarbital, induces the enzyme system in specific fetal tissues as well as in the placenta. The extent of enzyme induction is greatest in adult, less in neonatal tissues, and least in fetal tissues. Induction of hydroxylase activity by 3-methylcholanthrene occurs in the liver, lung, and kidney of the adrenalectomized or hypophysectomized male rat, and the hepatic enzyme is induced by phenobarbital in the adrenalectomized male rat. The magnitude of aryl hydrocarbon hydroxylase induction varies greatly with the tissue and species-from no induction to more than 100-fold increases in enzyme activity. The enzyme system is also present and inducible in fetal cell cultures derived from whole hamster, mouse, rat, and chick. Further, hydroxylase activity is inducible in cell cultures derived from hamster fetal liver, lung, small intestine, and limbs, and in mouse 3T3 culture, an established cell line. © 1969.