Receptor analysis: An arithmetic correction improves precision and accuracy

Data of receptor analysis by ligand binding experiments should be processed using the formula DCORR = (B1 - B2.F1/F2)/VS.DCORR is an estimate of the concentration of receptor-bound radioligand; B1 and F1 are estimates of bound and free radioligand in assay 1; B2 and F2 are the corresponding values obtained from the parallel assay 2, which contains an additional excess of nonlabeled ligand; VS is the volume of assays 1 and 2 that was submitted to separation. DCORR will be superior to the conventional formula, D = (B1 - B2)/VS, if the radiolabeled receptor-ligand complexes are incompletely separated from nonspecifically bound and free radioligands. DCORR corrects for the systematic underestimation of the specifically bound radioligand implicated in D as well as for random errors due to imprecise pipetting during preparation of the parallel assays. The superiority of DCORR over D is verified by processing the data of androgen receptor analyses using agar gel electrophoresis for separation of bound and free radioligand.