Measuring the affinity of a radioligand with its receptor using a rotating cell dish with in situ reference area

This report describes a semi-automated method for the measurement of affinity of radiolabeled ligands interacting with cell-surface receptors on intact cancer cells. The method saves labor time and reagents compared to common manual measurements. A complete affinity measurement can be performed in one cell dish by using a target cell area and a reference area and repeatedly measure the differential activity (i.e. target activity—reference activity). The affinities obtained for different ligand–receptor interactions agreed with affinities reported in the literature.