Cataract induction by 1,2-naphthoquinone. II. Mechanism of hydrogenperoxide formation and inhibition by iodide.
Naphthalene cataract is probably due to peroxide production through naphthoquinone (NQ) redox cycling and/or glutathione conjugation. Both mechanisms yield losses of essential SH-groups in cristallins and are thus probably involved in protein modification finally visible as lens opacity. 1,2-Naphthoquinone produces H2O2 in the presence of either ascorbate, glutathione, NADH or--to a lesser extend--by homogenates of lens protein preparations. In the presence of 1,2-naphthoquinone and the above reductive additions, both, oxygen uptake and H2O2 formation can be observed. Reductive oxygen activation in these systems are diminuated by iodide in a concentration-dependent manner. Since maleimide-treated proteins are less capable to activate oxygen by 1,2-naphthoquinone, a direct oxygen activation by the interactions of 1,2-naphthoquinone with protein-SH is indicated. Catalysis of "diaphorase"-type (dia) enzymes via NADH--dia--1,2-NQ--O2 seems not to operate in hydrogenperoxide production during 1,2-naphthoquinone lens toxicity.
Kröner
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Institut für Botanik und Mikrobiologie, Technische Universität München, Bundesrepublik Deutschland.
Kleber
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Elstner
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EF
D000818:Animals; D002386:Cataract / Q000139:chemically induced*; D002417:Cattle; D003459:Crystallins / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007454:Iodides / Q000494:pharmacology*; D007700:Kinetics; D009285:Naphthoquinones / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects*
D003459:Crystallins; D007454:Iodides; D009285:Naphthoquinones; C040756:1,2-naphthoquinone; D006861:Hydrogen Peroxide