The effect of the administration of cobaltic protoporphyrin IX on drug metabolism, carbon tetrachloride activation and lipid peroxidation in rat liver microsomes

The effects of cobaltic protoporphyrin IX (CPP) administration on hepatic microsomal drug metabolism, carbon tetrachloride activation and lipid peroxidation have been investigated using male Wistar rats. CPP (125 μmol/kg, 72 h before sacrifice) profoundly decreased the levels of hepatic microsomal heme, particularly cytochrome P-450. Consequently, the associated mixed-function oxidase systems were equally strongly depressed. An unexpected finding was that CPP administration also greatly decreased the activity of NADPH/cytochrome c reductase, a result not generally found with the administration of the more widely used cytochrome P-450 depleting agents, cobaltous chloride. Activation of carbon tetrachloride, measured as covalent binding of [¹⁴C] CCl₄, spin-trapping of CCl₃ and CCl₄-stimulated lipid peroxidation, was much lower in liver microsomes from CPP-treated rats. Other microsomal lipid peroxidation systems, utilising cumene hydroperoxide or NADPH/ADP-Fe²⁺, were also depressed in parellel with the decrease in microsomal enzyme activities.