Graphical orientation procedure for the estimation of Kd and Bmax values of ligand binding to two receptor subpopulations.

Within a few minutes, the procedure described here provides to the investigator, performing binding studies, information about Kd and Bmax values of two possibly present receptor subpopulations. The procedure is based on the comparison of the experimental curve with values of ligand binding to only one receptor population at 4 defined levels of radioligand binding. The binding parameters are derived from comparison of 4 horizontal deviations at these levels with tabulated deviations. Kd and Bmax values can be further confirmed by comparison of the experimental data with the simulated binding curve obtained by entering the binding parameters found in the formula for ligand binding to two receptor subpopulations. The practical use of this procedure was demonstrated both for simulated and for experimental data; it was confirmed by comparison with binding parameters obtained by computer programs used for the evaluation of receptor heterogeneity.