title: Radioimmunoassay of beta lipoprotein-protein of rat serum.
abstract: A double antibody radioimmunoassay for rat serum beta lipoprotein-protein (beta Lp-protein) is described. The protein was purified by ultracentrifugation, selective heparin-manganous precipitation, and gel filtration on Sephadex G-200. Antiserum was prepared in rabbits by biweekly immunization and absorbed with nonbeta lipoprotein containing rat serum. Iodination with (125)I and purification by gel filtration provided a radiolabeled protein which was > 98% displaced by purified beta lipoprotein in the immunoassay. The radioimmunoassay was sensitive to beta Lp-protein concentrations from 0.1 to 1.5 mug. Specificity of the immunoassay for beta Lp-protein was established by comparison of the displacement curves obtained with serum very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL), and density (d) > 1.21 fractions and with the beta and alpha migrating lipoproteins eluted from paper electrophoretograms. Suitability of the assay for measuring beta Lp-protein in serum was established by demonstrating 100% recovery of beta lipoprotein added to whole serum and by the absence of immunoreactive beta Lp-protein in serum of orotic acid-treated rats. Examination of sera from six other vertebrates species revealed partial cross-reactivity. Normal rat serum was found to contain 0.25+/-0.01 mg/ml of beta Lp-protein and hepatic production by an isolated perfused rat liver system was determined as 0.145 mg/hr.
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000032:analysis*; D002850:Chromatography, Gel; D010856:Columbidae; D004285:Dogs; D005260:Female; D006168:Guinea Pigs; D000882:Haplorhini; D006801:Humans; D007106:Immune Sera; D007122:Immunoelectrophoresis; D007456:Iodine Isotopes; D008074:Lipoproteins / Q000096:biosynthesis / Q000097:blood* / Q000302:isolation & purification; D051379:Mice; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D013045:Species Specificity; D014461:Ultracentrifugation
chemical_list: D001798:Blood Proteins; D007106:Immune Sera; D007456:Iodine Isotopes; D008074:Lipoproteins