Tocopherol contents of lipoproteins from frozen plasma separated by affinity chromatography

We investigated whether freezing and storage of plasma altered alpha-tocopherol levels of whole plasma or the lipoprotein fractions derived from such plasma. Plasma from 24 men, at each of two collection periods, was frozen at -20 degrees C for six weeks, then high-density lipoproteins (HDL) were separated from low- plus very low-density lipoproteins (LDL-VLDL) by heparin affinity chromatography. Whole plasma and the lipoprotein fractions were analyzed for alpha-tocopherol content and compared to counterparts from fresh plasma. Freezing and storage did not reduce alpha-tocopherol levels of plasma or the lipoprotein fractions. alpha-Tocopherol values from fresh and frozen plasma were highly correlated for both plasma (period 1, r = 0.94; period 2, r = 0.93) and the LDL-VLDL fractions (periods 1 and 2, r = 0.97). Percent distribution of alpha-tocopherol between the two lipoprotein fractions was comparable for lipoproteins derived from fresh and frozen plasma. Under the storage conditions used in this study, plasma can be frozen for at least six weeks prior to lipoprotein fractionation with no detectable detrimental effects on alpha-tocopherol content of either plasma or lipoproteins.