Abstract
A new colorimetric method for the determination of serum lipid peroxide, free of the interference from sialic acids, was established. Then serum lipid peroxide values of 129 healthy controls and 117 patients with cerebrovascular diseases were determined by the new method.
In the procedure elaborated, serum lipid peroxide was precipitated with protein adding 5 volumes of 20°trichloroacetic acid to 0.5 ml of serum. After centrifugation at 3, 500 rpm for 10 min, the supernatant was decanted and the precipitate was washed once with 0.1N sulfuric acid. Then 2.5 ml of 0.1N sulfuric acid and 3.0 ml of 0.2% thiobarbituric acid (TBA) dissolved in 2M sodium sulfate were added to this precipitate, and reaction of lipid peroxide with TBA was performed by heating in boiling water bath for 30 min. After cooling in cold water, resulting chromogen was extracted with 4.0 ml of n-butyl alcohol by vigorous shaking. This was followed by centrifugation at 3, 000 rpm for 10 min and optical density of the organic phase was determined at the wavelength of 530 nm. In the new method, TBA reaction was performed in a weak acid medium, this was thought to inhibit the formation of TBA-reactive aldehyde derivatives of sialic acids. Besides presence of sodium sulfate might contribute to the elimination of the interference from sialic acids by depressing the rate of reaction with TBA through its enhancing effect on the ionic strength of the reaction mixture. This method was specific and useful for precise measurements of serum lipid peroxide.
Average serum lipid peroxide value in healthy controls was 3.6±0.87 nmol/ml. In controls, the value of those under 49 years of age was significantly lower as compared with those aged 50-59 and over 60. The average values of patients with cerebral infarction and cerebral hemorrhage were 4.5 ± 1.53 nmol/ml and 4.4±1.08 nmol/ ml, respectively, these values were significantly higher than that of controls. When classified by age, the difference between patients and controls was obvious in age groups of under 59. In controls, significant inverse relationship was observed between serum lipid peroxide and tocopherol.
These results may indicate the important role of lipid peroxide in cerebrovascular diseases and aging process. Although precise causal mechanism about the incrimination of lipid peroxide in cerebrovascular diseases was unclear, the possibility of its relation with platelet hypersensitivity and thrombotic vascular damage was envisaged.
