[Binding of tritiated imipramine to human platelets. 1 or several binding sites?]

Using Langers' method (10) under their laboratory conditions, the authors determined the characteristics of the high-affinity imipramine-binding site on human platelets in thirty-five normal subjects, equally divided between the sexes and distributed by decade from twenty to sixty years of age and above. Bmax was 440 +/- 121 fmol./mg. protein, Kd 0.96 +/- 0.62, 10(-9) M. Protein concentration was held within a range of 0.2 to 0.55 mg./ml. in order to avoid nonlinear bias with Bmax, expressed in fmol./ml. of incubate. The characteristics of the site did not co-vary with sex or age in this experimental series. However, subject to additional investigation, the curve of the Scatchard graph would seem to indicate the possible existence of a distinct, low-affinity imipramine-binding site.