Abstract
Determination of apoB by rate nephelometry is a simple, rapid and precise method, which is also suitable for a routine laboratory. It can be standardized with lipoprotein-B or LDL fractions, but only if these fractions are diluted with fresh whole serum. The standardization is also valid for VLDL if the samples are diluted with hydroxypolyethoxydodecane (trade name: Thesit) in a concentration of 0.33 g/liter. Using rate nephelometry, a strong correlation between the contents of cholesterol and apoB of VLDL as well as of LDL can be demonstrated. Similar high correlations are achieved if apoB is determined chemically in isolated lipoprotein fractions. The ratio of apoB to cholesterol is constant but not the same in both VLDL and LDL. There is also a strong correlation between the concentration of apoB in whole serum with the LDL cholesterol values in a normotriglyceridemic population. Therefore, the assay of apoB in whole serum by rate nephelometry is proposed as a screening method for dyslipoproteinemia (increased concentrations of atherogenic lipoproteins at normal or elevated levels of cholesterol in plasma).
Highlights
Determination of apoB by rate nephelometry is a simple, rapid and precise method, which is suitable for a routine laboratory
It can be standardized with lipoprotein-B or low density lipoprotein (LDL) fractions, but only if these fractions are diluted with fresh whole serum
The assay of apoB in whole serum by rate nephelometry is proposed as a screening method for dyslipoproteinemia.-Wieland, H.,P
Summary
A Beckman L 5-75 model ultracentrifuge was operated at 10°C. For preparative purposes, fresh plasma from healthy blood donors was ultracentrifuged for 24 hr at 50,000 rpm in a type 60 TI rotor. Samples were recovered after grinding the agarose strips and removing the agarose by ultracentrifugation in a 50 T I rotor for 2 hr at 40,000 rpm This was performed according to the method of Scheidegger [27] using pre-cast agarose plates (Lipidophor, Immuno-Diagnostika, Heidelberg, F.R.G.). Before protein determination the L D L fractions (d 1.03-1.06 g/ml) were analyzed by PAGE after extraction with tetramethylurea (TMU) [29] and by immunoelectrophoresis against anti-human serum obtained from Behringwerke (Marburg/Lahn, F.R.G.). Lipoprotein B (Lp-B) was used as an antigen It was isolated by preparative isoelectric focusing of the d < 1.21 g/ml fraction of fresh plasma, obtained after dialysis against phosphate-buffered 0.075 M NaC1, p H 7.3. The same serum in three different dilutions was used daily as a secondary standard
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