HEME OXYGENASE ACTIVITY AND CYTOCHROME-P-450 CONTENT ASSOCIATED WITH INDUCED METALLOTHIONEIN IN THE LIVER OF RATS TREATED WITH VARIOUS METALS

The relationship between heme oxygenase (HO) activity and metallothionein (MT) concentration in rat liver was investigated. The responses to treatments with metals of the A-series metals that can bind to MT in vivo (e.g., cadmium, zinc and copper) and the B-series metals that cannot bind to MT in vivo (e.g., cobalt, nickel and manganese) were compared. A single treatment with any metal in the A- or B-series increases both hepatic HO activity and MT concentration. However, repeated treatments with A-series metals decreases HO activities more than a single injection despite appreciable increases in MT concentrations. Repeated treatments with B-series metals increase both HO activities and MT concentrations. On the other hand, cytochrome P-450 concentrations are depressed by single or repeated treatments with all metals tested. These results suggest that the binding abilities of metals to MT in vivo, or the replaceable zinc concentration in MT, affect the magnitude of HO activity.