Comparison of ultrafiltration and equilibrium dialysis for estimation of protein binding

Introduction: Protein binding of tracer to plasma proteins influences the equilibrium between tracer in brain and blood, and to obtain truly quantitative and unbiased measures of receptor binding, the binding potential relative to free unmetabolized tracer in plasma (BPF) must be obtained. The measurement of protein binding is however laborious and noisy and is often disregarded. Equilibrium dialysis (ED) with passive diffusion across a semipermeable membrane is regarded as the gold standard and this study compares this time-consuming method with the faster ultrafiltration (UF) method.