Regulation of Heme Oxygenase Activity in Rat Liver during Oxidative Stress Induced by Cobalt Chloride and Mercury Chloride

P. A. Kaliman^*, I. V. Nikitchenko, O. A. Sokol, and E. V. Strel'chenko

Department of Biochemistry, Karazin Kharkov National University, pl. Svobody 4, Kharkov, 61077 Ukraine; fax: (0572) 47-1816; E-mail: Pavel.A.Kaliman@univer.kharkov.ua

^* To whom correspondence should be addressed.

Received April 24, 2000; Revision received July 27, 2000

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Activities of heme oxygenase and tryptophan-2,3-dioxygenase and cytochrome P450 content in liver as well as absorption of the Soret band and optical density at 280 nm in serum were determined 2 and 24 h after administration of HgCl₂ and CoCl₂ and after co-administration of the metal salts with alpha-tocopherol. Administration of HgCl₂ and CoCl₂ increased the contents of hemolysis products in the serum, induced heme oxygenase, and decreased cytochrome P450 content in the liver. Injection of HgCl₂ increased the activity of tryptophan-2,3-dioxygenase holoenzyme and enzyme saturation with the heme, but administration of CoCl₂ decreased these parameters. Pretreatment with alpha-tocopherol completely blocked the changes induced by HgCl₂ after 24 h. Induction of heme oxygenase induced by CoCl₂ was not blocked by alpha-tocopherol, but this antioxidant normalized the increase in the level of hemolysis products in the serum and decrease in tryptophan-2,3-dioxygenase holoenzyme activity and cytochrome P450 content. Mechanisms of regulation of heme oxygenase by mercury and cobalt ions are discussed.

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KEY WORDS: heme oxygenase, tryptophan-2,3-dioxygenase, mercury chloride, cobalt chloride, alpha-tocopherol, oxidative stress

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