On the role of lipid peroxidation and protein-bound aldehydes in the haloalkane-induced inactivation of microsomal glucose 6 phosphatase.
The inactivation of liver microsomal glucose 6 phosphatase induced either by Fe2+ or by haloalkanes (CCl4, CBrCl3) was investigated in NADPH-microsomes systems. In the case of haloalkanes, EDTA was included in the incubation mixtures, so to exclude participation of free Fe2+ in the ensuing lipid peroxidation. Microsomal glucose 6 phosphatase activity was measured along with the release of malonic dialdehyde and the appearance of carbonyl products bound to microsomal protein, taken as indices of the peroxidative process. Fe2+ was added to NADPH-microsomes at different concentrations, one (6 microM) resulting in an extent of lipid peroxidation comparable with that induced by haloalkanes, the other (60 microM) representing a situation of excess Fe2+, leading to massive lipid peroxidation. Inhibition of glucose 6 phosphatase caused by 6 microM Fe2+ was comparable to that induced by haloalkanes in EDTA-microsomes systems, which supports the view that lipid peroxidation--rather than covalent binding of free radical metabolites--represents the main event leading to the inactivation of glucose 6 phosphatase caused by haloalkanes. The production of 4-hydroxynonenal--the known toxic product of lipid peroxidation--was also studied. A remarkable accumulation of 4-hydroxynonenal was observed in the microsomal membranes after peroxidation induced by 6 microM Fe2+ or haloalkanes, as compared to the incubation medium. In addition, experiments carried out with CCl4 and CBrCl3 in vivo suggested the possible existence of a cytosolic detoxification system able to remove lipid-derived carbonyls bound to microsomal protein.
Fulceri
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Istituto di Patologia Generale dell'Università di Siena, Italy.
Pompella
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Benedetti
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Comporti
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D000447:Aldehydes / Q000378:metabolism*; D000473:Alkanes / Q000494:pharmacology*; D000818:Animals; D004789:Enzyme Activation; D005952:Glucose-6-Phosphatase / Q000378:metabolism*; D006219:Halogens / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D000447:Aldehydes; D000473:Alkanes; D006219:Halogens; D005952:Glucose-6-Phosphatase; C027576:4-hydroxy-2-nonenal