Effect of low temperature storage on the alpha-tocopherol (vitamin E) content of human lipoproteins determined by high-performance liquid chromatography

Plasma lipoproteins contain a great amount of a-tocopherol (Vitamin E). To track the metabolism of this antioxidant in the human organism a great numb er of blood samples should be analysed. In order to improve the time consum ing work-up of samples, the effect of low temperature storage on the consta ncy of alpha -tocopherol concentration in plasma and freshly separated lipo proteins have been studied by highperformance liquid chromatography (HPLC). We have established that up to the 42nd day there is no change both in the total tocopherol concentration of plasma and in the tocopherol content of lipid fractions. The sum of alpha -tocopherol concentrations, measured in t he lipid fractions, always returned the 99.0 +/- 1.11% of the alpha -tocoph erol concentration found in plasma, Under the storage conditions used this study, after six weeks the decrease of content in the high density lipoprot ein (HDL) fraction was 26.6% (p < 0.01) while that in the low and very low density lipoprotein (LDL+VLDL) fraction was much smaller (3.3%, ns.). Using this simple and economic method the distribution of alpha -tocopherol in t he lipid fractions can be determined within 42 days without any loss. This procedure enables us to measure precisely the a-tocopherol concentration of the plasma and any of the lipid fractions. The determination of alpha -toc opherol concentration is only necessary for the plasma and one of the lipid fractions since the alpha -tocopherol concentration of the other lipid fra ction can be calculated.