Cadmium-induced alteration of the microsomal mono-oxygenase system in male rat liver: Effects on hemoprotein turnover and phospholipid content

Abstract

After cadmium treatment (2.0 mg Cd/kg, i.p.) a marked inhibition is observed in microsomal drug metabolizing enzyme activity which is correlated with a reduction in the hemoprotein, cytochrome P-450, content. Incorporation of the heme precursor, 3H-δ-aminolevulinic acid ( 3H-δ-ALA), into microsomal CO-binding particles was decreased in cadmium-treated rats. Cadmium treatment produced a differential effect in the biphasic disappearance of radioactivity from the CO-binding particles in that the metal decreased the half-life of the fast-phase component and increased the half-life of the slow-phase component. Thus, the reduction in microsomal levels of cytochrome P-450 induced by cadmium apparently results from a stimulation of the degradation of the fast-phase hemoprotein fraction and a reduction in the synthesis of the slow-phase and fast-phase hemoprotein fractions. Cadmium treatment did not quantitatively alter microsomal phospholipid content.