(A) Scatchard plot analyses of mOSM binding to LO cells. LO cells were incubated with various concentrations of¹²⁵I-labeled mOSM in the presence or absence of a 1,000-fold excess of unlabeled mOSM. After 3 hours of incubation at 4°C, free mOSM was washed out through a Whatman GF/C glass filter (Maidstone, UK), and the bound radioactivity was measured by a gamma counter. Specific binding was obtained by subtracting nonspecific binding from total binding. Data are plotted according to the Scatchard transformation using the LIGAND program. Each point represents the average of duplicate measurements. The analyses clearly show two distinct affinities. (B) Cross-linking experiment using LO cells. LO cells were incubated with 5 nmol/L ¹²⁵I-mOSM in the presence or absence of a 1,000-fold excess of unlabeled mOSM. After 4 hours of incubation at 4°C, cross-linked proteins were analyzed by SDS-PAGE.