WHETHER CYTOCHROME-P450 INDUCTION ACCOMPANIES GLUCURONOSYL AND GLUTATHIONE TRANSFERASE INDUCTION BY ISOMERS OF DIPYRIDYL APPEARS UNRELATED TO DOSE AND IRON CHELATION PROPERTIES

Administration of 4,4'dipyridyl to rats induces the activities of xenobiotic transferases (phase II drug metabolizing enzymes), UDP-glucuronosyl-transferase and glutathione-S-transferase, and also the concentration and activity of cytochrome P450 (a phase I drug metabolizing enzyme). 2,2'Dipyridyl, an isomer possessing iron chelation properties, only induces the phase II enzymes. Although the magnitude of the phase II induction by 2,2'dipyridyl increases with increasing dosages, the selective induction of only phase II activities remains inviolate. Co-administration of 2,2'dipyridyl does not prevent 4,4'dipyridyl from inducing cytochrome P450, suggesting that the iron chelation property is not the factor that precludes 2,2'dipyridyl from coordinately inducing cytochrome P450 with the transferases.