Effects of EDTA on Stability of Drug Metabolizing Enzymes in Liver Microsomes of Rats

Kamataki, Tetsuya; Kitagawa, Haruo

doi:10.1248/cpb.22.1041

Cited by 14 publications

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“…We have already reported that drug metabolizing activities are quite sensitively affected by lipidd peroxidation (15,16). As can be seen in the same figure, the apparent activity of ethyl morphine N-demethylase was found to change inversely in response to the change in lipid peroxidation.…”

Section: Resultssupporting

confidence: 63%

“…Daiichi Pure Chemicals Co., Tokyo, Japan, and the 0.67 ° ; solution was prepared as described previously (15). NADP, glucose 6-phosphate and glucose 6-phosphate dehydrogenase (EC 1.1.1.49, Grade 1) were purchased from Boehringer Mannheim Co.…”

Section: Methodsmentioning

confidence: 99%

“…Japan, were fasted for about 18 hr prior to sacrifice. The microsomes front rat livers were prepared as reported previously (15). The microsomal suspensions were prepared by homogenizing microsomal pellets gently with 1.15 % KCI solution, and used on the day of preparation.…”

Section: Methodsmentioning

confidence: 99%

“…Lipid peroxides formed were determined by the thiobarbituric acid (TBA) method as pre viously reported (15). The formation of lipid peroxides was represented by calculating optical density at 532 nm per mg of microsomal protein per ml of incubation mixture.…”

Section: Methodsmentioning

confidence: 99%

“…Such was suggested by the observation that drug metabolizing enzyme activities respond with a high degree of sensitivity to lipid peroxidation (12,(15)(16)(17)(18).…”

mentioning

confidence: 99%

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Stimulative Effects of Chelating Agents, 2, 2’-Bipyridine and 1, 10-Phenanthroline, on Lipid Peroxidation in Rat Liver Microsomes

Kamataki

Ozawa

Kitada

et al. 1977

Japanese Journal of Pharmacology

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Abstract--Well known lipid peroxidation inhibitors, 1,10-phenanthroline and 2,2' bipyridine, stimulated microsomal NADPH and ascorbic acid-dependent lipid peroxi dation when low concentrations of these chelating agents were added to incubation mixture. The stimulatory effects of the chelating agents on lipid peroxidation were enhanced when ferrous ion was added together with the chelating agents to the mixture at a molar ratio of I : 1. Ethylenediaminetetraacetic acid (EDTA) had no stimulatory effect on lipid peroxidation.Ferrous ion-EDTA complex increased lipid peroxidation by only 20-30'/(), which was lower than that obtained by addition of the same con centration of ferrous ion alone. On the other hand, manganese and calcium ions, which are also inhibitors of lipid peroxidation, had no ability to stimulate lipid peroxidation even in the presence of extra ferrous ions. Changes in the lipid peroxidation by chelating agents affected the apparent activity of ethylmorphine N-demethylation.Although the physiological roles of the peroxidation of unsaturated fatty acids of liver microsomal phospholipids have yet to be confirmed, numerous reports have suggested that the reaction is the cause of hepatotoxicity of carbon tetrachloride (1, 2). Concerning the nature of NADPH-dependent lipid peroxidation, NADPH is the sole source of electrons, and cannot be replaced by the other pyridine nucleotide, NADH (3). The reaction requiring iron in either ferric or ferrous form (1, 4), is stimulated by nucleoside pyrophosphate, es pecially ADP, and inorganic pyrophosphate (3, 5, 6), and is inhibited by metal ions such as manganese, cobalt and calcium ions (7), chelating agents such as EDTA, 1,10-phen anthroline and 2,2'-bipyridine (6), various drugs (8, 9) and an unknown factor(s) in the cytosol of livers (10-12). Hochstein et al. (3, 5) have demonstrated that the stimulative effects of the pyrophosphate on microsomal lipid peroxidation are due to the ferrous ion pyrophosphate complex. More recent work by Pederson and co-workers (13, 14) has shown that NADPH-dependent lipid peroxidation of extracted microsomal lipids by purified NADPH-cytochrome c reductase required ferrous ion-EDTA complex, and that EDTA could not be substituted by other chelating agents such as 1,10-phenanthroline or citrate.This study was thus initiated in order to examine further the effects of chelating agents on microsomal lipid peroxidation.In addition, changes in drug metabolizing enzyme ac tivity induced by lipid peroxidation were also determined in an attempt to provide further data that certain chelating agents inhibit or stimulate lipid peroxidation, depending upon the concentrations used. Such was suggested by the observation that drug metabolizing

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Section: Resultssupporting

confidence: 63%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…Such was suggested by the observation that drug metabolizing enzyme activities respond with a high degree of sensitivity to lipid peroxidation (12,(15)(16)(17)(18).…”

mentioning

confidence: 99%

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