Aim An enzyme linked immunosorbent assay (ELISA ) using HRP-conjugated rabbit antihurnan plasma apo B₁₀₀ IgG was develoPed for measurement of low density liPoprotein(LDL) receptors on purified rabbit liver plasma membranes.Methods Membrane protein adhered to tbe solid phase by an overnight incubation, and was quantified by measuring the protein concentrations te fore and af-ter coating. A curve of anti-apo Bloo bo binding to known amounts of LDL was constructed to quantify the LDL bound. Parallel samples with 25-fold excess rabbit plasma LDL were assay6d to detect nonsPeCific binding.Results Kd and Bmax, worked out by scatchard plot, were l3. 59 mg/L and l24 ng/g membrane pro-tein(n= 5),re8PeCtively.C.ncluslous The results support the use of ELISA to measure LDL receptors, particularly for physiologic studies.