Assay of Total Plasma Apolipoprotein B Concentration in Human Subjects

Abstract

A B S T R A C T We have developed a double antibody radioimmunoassay (RIA) for human apolipoprotein B (ApoB). The assay measures not only the ApoB content of 8-lipoproteins (low density lipoproteins [LDL]) but also that contained in the other lipoproteins in plasma.Purified lymph and plasma chylomicrons and plasma very low density lipoproteins (VLDL) produced displacement curves in the assay system which paralleled those produced by pure LDL. Thus, the ApoB found in chylomicrons, VLDL, and LDL were immunologically identical. ApoB accounted for about 25 and 35%, respectively, of the total protein of chylomicrons and VLDL by RIA. VLDL and LDL preparations from normal and hyperlipoproteinemic subjects also produced parallel displacement curves, suggesting that the ApoB of normal and hyperlipoproteinemic subjects were immunologically identical. High density lipoproteins and abetalipoproteinemic plasma displaced no counts, nor did the sera of several animal species produce any useful displacement curves in this system.The fasting total plasma ApoB concentration of normal subjects was 83±16 mg/dl (mean+SD). ApoB levels were high in Type II (162±16), and less so in Type IV (112±24) and Type V (105±17). When plasma ApoB concentration in Type IV patients was graphed against plasma glycerides, two subpopulations, which may represent different genetic or biochemical subgroups, were apparent. ApoB concentration in individuals on constant diet and drug regimen was stable over weeks to months. Greater than 90% of ApoB of normal and Type II subjects was in the d> 1.006 plasma fraction. By contrast, only 50-80% of ApoB was in the d > 1.006 fraction in Types IV and V. Thus, hypertriglyceridemia was associated primarily with a redistribution of ApoB to the lighter density fractions; by contrast, in hypercholesterolemia absolute ApoB concentration was markedly increased.

Associations between HDL-cholesterol and polymorphisms in hepatic lipase and lipoprotein lipase genes are modified by dietary fat intake in African American and White adults

“…ApoA-I was determined by a modified radioimmunoassay (30,31). ApoB was determined by radioimmunoassay (32), with minor modifications.…”

Associations of lipoprotein cholesterols, apolipoproteins A-I and B, and triglycerides with carotid atherosclerosis and coronary heart disease. The Atherosclerosis Risk in Communities (ARIC) Study.

“…23 ApoA-I was determined by a modified radioimmunoassay 26,27 \y e n a v e previously shown the assay to be specific for apoA-I, accurate in recovery experiments and in comparison with a consensus value, and reliable in frozen plasma specimens. 28 The apoB radioimmunoassay of Schonfeld et al 29 was used with minor modifications. LDL standard and tracer were prepared by zonal ultracentrifugation.…”

Plasma lipid, lipoprotein cholesterol, and apoprotein distributions in selected US communities. The Atherosclerosis Risk in Communities (ARIC) Study.

“…Radioimmunoassay procedures were used for apoprotein A-I 22 and apoprotein B according to Schonfeld et al 23 with minor modifications. 24 These assays were suitable for specificity, recovery, accuracy, and reliabil- 53 55 49 53 58 58 45 48 46 52 56 54 59 59 10 51 55 60 61 55 60 66 69 53 54 56 56 66 63 69 70 Percentile 50 85 92 101 98 92 105 113 123 91 104 102 95 124 122 124 124 90 148 178 175 180 182 212 228 237 189 217 199 189 265 244 250 250 95 164 203 215 226 229 287 273 295 235 249 244 215 326 298 309 312 Values are in milligrams per deciliter.…”