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Free radical effects on myocardial membrane microviscosity
1Department of Medical Physiology and Biochemistry, Faculty of Medicine, University of Stellenbosch, Tygerberg, Republic of South Africa.
Cardioscience
|December 1, 1993
Summary
This study investigated how free radicals affect heart cell membranes. Results suggest that free radicals, particularly those produced during ischemia, significantly alter membrane microviscosity and fluidity.
Area of Science:
- Biochemistry
- Cardiovascular Physiology
- Cell Biology
Background:
- Myocardial ischemia causes significant changes in myocardial membrane microviscosity.
- The role of free radical production and lipid peroxidation in these changes remains unclear.
Purpose of the Study:
- To investigate the in vitro effects of two free radical generating systems on the microviscosity of cardiac membranes.
- To assess the contribution of lipid peroxidation to free radical-induced changes in membrane microviscosity.
Main Methods:
- Isolated sarcolemmal, mitochondrial, and sarcoplasmic reticulum membranes were exposed to hydrogen peroxide/iron chloride (H2O2/FeCl2) and xanthine oxidase/hypoxanthine/iron chloride (XO/HX/FeCl3) systems.
- Malondialdehyde (MDA) formation, an indicator of lipid peroxidation, was quantified using the thiobarbituric acid test.
- Changes in membrane microviscosity were measured in response to free radical exposure.
Main Results:
- Both radical generating systems induced malondialdehyde formation in all three membrane types.
- Sarcolemmal membranes showed higher sensitivity to H2O2 damage, while mitochondrial membranes exhibited greater malondialdehyde production with the xanthine oxidase system.
- H2O2/FeCl2 decreased microviscosity (increased fluidity) in all membranes. The xanthine oxidase system increased mitochondrial and sarcolemmal microviscosity but decreased sarcoplasmic reticulum microviscosity.
Conclusions:
- Free radical production, particularly from the xanthine oxidase system, significantly alters cardiac membrane microviscosity.
- The observed in vitro changes in membrane microviscosity induced by xanthine oxidase resemble those seen in ischemia.
- This suggests a potential causal role for superoxide and hydroxyl free radicals generated during ischemia in altering myocardial membrane properties.