Effect of continuous treatment with some heavy metal salts upon rat hepatic monooxygenases

The effect of 90-days treatment with Co(NO3)2, NiSO4, CdSO4, ZnSO4 and HgCL2 on the rat liver cytochrome P-450 linked monooxygenases was studied. It was found that all metal salts studied significantly decreased the activity of ethylmorphine N-demethylase in the rat liver. The activity of benzphetamine N-demethylase was decreased by the salts of Co, Cd and Zn whereas Hg and Ni did not change it. Hepatic microsomal cytochrome P-450 content was significantly decreased after treatment with Co, Cd, Zn and Ni and was not changed by Hg. Microsomal hem content was decreased by Co, Cd and Zn and was not changed by Ni and Hg. Co, Cd, Zn and Ni salts decreased the activity of 5-aminolevulinic acid synthetase which shows that the decreased cytochrome P-450 content was probably due to a decrease of its synthesis. HgCL2 had no enzyme inhibitory effect. All metal salts did not change the metabolizing activity of aniline hydroxylase which confirm that multiple molecule species of cytochrome P-450 exist in the liver of adult rats. The hepatic cytochrome b5 content was not changed by the metal salts studied which shows that probably cytochrome b5 was not involved in the enzyme inhibitory action of heavy metal salts on the rat liver monooxygenases.