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Glutathione-dependent protection by rat liver microsomal protein against lipid peroxidation
Abstract:
GSH is an important cellular defense against oxidant injury. Its effect in the rat liver microsomal lipid peroxidation system has been examined. Incubation of fresh rat liver microsomes with ascorbic acid and ADP-chelated iron leads to the peroxidation of microsomal lipids (production of thiobarbituric acid-reactive substances and destruction of polyunsaturated fatty acids) following a 2 to 5 min lag. Addition of 0.1 mM GSH to the system lengthened the lag period by 5 to 15 min without affecting the rate or the extent of lipid peroxidation. GSH could not be replaced in prolonging the lag by cysteine, mercaptoethanol, dithiothreitol, propylthiouracil, or GSSG. The GSH effect on the lag was abolished by heating or trypsin digestion of the microsomes, indicating that microsomal protein is required for its expression. Progressively longer lags were observed as the GSH concentration was increased from 0.1 to 5 mM, but there was no evidence of GSH oxidation as a consequence of the protection against lipid peroxidation. GSH protected against heat inactivation of the microsomal protein responsible for the GSH effect. Experiments with an oxygen electrode revealed that the GSH protection did not alter the ratio of O2 consumed to thiobarbituric acid-reactive substances produced. This implicated free radical scavenging as the mechanism of protection. These results indicate the existence of a GSH-dependent rat liver microsomal protein which scavenges free radicals. This protein may be an important defense against free radical injury to the microsomal membrane.
Insights
Glutathione (GSH) prolongs the lag time in rat liver microsomal lipid peroxidation by scavenging free radicals. This protective effect is mediated by a heat-sensitive microsomal protein, highlighting GSH
Area of Science:
- Biochemistry
- Cellular Biology
- Oxidative Stress Research
Background:
- Glutathione (GSH) is a critical endogenous antioxidant involved in cellular defense mechanisms.
- Lipid peroxidation in rat liver microsomes is a key indicator of oxidative damage.
- Understanding the role of GSH in mitigating microsomal lipid peroxidation is essential for comprehending cellular protection.
Purpose of the Study:
- To investigate the specific effects of glutathione (GSH) on the rat liver microsomal lipid peroxidation system.
- To elucidate the mechanism by which GSH influences lipid peroxidation and identify the responsible cellular components.
Main Methods:
- Incubation of rat liver microsomes with ascorbic acid and ADP-chelated iron to induce lipid peroxidation.
- Addition of varying concentrations of GSH to measure changes in the lag period and lipid peroxidation extent.
- Utilized heat and trypsin digestion to assess the protein-dependent nature of GSH's effect and employed an oxygen electrode to analyze O2 consumption.
Main Results:
- GSH significantly lengthened the lag phase of lipid peroxidation without altering the rate or extent of the reaction.
- The protective effect of GSH was dependent on intact microsomal proteins and could not be replicated by other reducing agents or GSSG.
- GSH protected the responsible microsomal protein from heat inactivation, and oxygen consumption ratios indicated free radical scavenging as the mechanism.
Conclusions:
- A GSH-dependent protein in rat liver microsomes actively scavenges free radicals, thereby delaying lipid peroxidation.
- This protein represents a crucial defense mechanism against free radical-induced damage to the microsomal membrane.
- The findings underscore the vital role of glutathione-mediated antioxidant systems in protecting cellular structures from oxidative injury.