OXIDATION OF LOW-DENSITY LIPOPROTEINS LEADS TO DISTURBANCE OF THEIR BINDING WITH ALPHA-TOCOPHEROL

The dynamics of binding of exogenous alpha-tocopherol (alpha-T) added to native or oxidatively modified LDLs (LDLs or oxLDLs) were investiga ted. Venous blood from 31 clinically healthy blood donors (15 males an d 16 females) was used. LDLs were isolated by density gradient ultrace ntrifugation. LDLs were oxidized in vitro by CuSO4. LDLs or oxLDLs wer e enriched with exogenous alpha-T (initial concentrations: 0; 10; 20; 50; or 100 nmol per mg protein). The contents of alpha-T in LDLs or in oxLDLs were measured by HPLC. Lag-phase of LDL oxidation before or af ter saturation with alpha-T was recorded. Correlation analysis of the lag-phase of LDL oxidation and alpha-T content in LDLs was carried out by the method of Ester-bauer et al. The experimental results demonstr ated that: (i) alpha-T was incorporated into native LDLs to a higher e xtent as compared to oxLDLs. (ii) A saturation of LDLs and oxLDLs with alpha-T was observed. (iii) A positive correlation was observed betwe en the duration of the lag-phase of LDL oxidation in vitro and the con tent of alpha-T in LDLs. (iv) Based on LDL saturation with alpha-T, th e persons could be clasified in two groups: LDLs from group I of 26 pe rsons were found to incorporate exogenous alpha-T to the extent of 1.8 to 3 times its initial concentration; LDLs from group II of 5 persons incorporated little or no exogenous alpha-T. In the first group, oxid ation of LDLs lead to a considerable decrease in alpha-T-dependent var iable k and to a moderate reduction of alpha-T-indepeudent variable a in the equation of Ester-bauer et al.: lag-phase k . [alpha-tocopherol ] + a. In the second group, oxidation of LDLs lead to insignificant ch anges in k, as well as in a. (V) According to the levels of k and a th e native LDLs from the second group of 5 persons were very close to ox LDLs from the first group of 26 persons. Presumably, native LDLs from the second group of persons were initially oxidatively modified, and p robably this will be a risk group in relation to atherogenic disorders .