Journal of Clinical Endocrinology & Metabolism, Vol 53, 502-506, Copyright © 1981 by Endocrine Society

ARTICLES

Fluorescein-isothiocyanated insulin interactions with human platelets

R Shimoyama

The interactions of fluorescein-isothiocyanated porcine insulin (FITC- insulin) with human platelets were examined by a fluorescence polarization technique. The degree of polarization of the incubation mixture of FITC-insulin and platelets was changed by the ratio of bound to free insulin. This method enabled us to follow the time course of the reaction in the homogeneous assay system without separating the insulin-receptor complex, and it was shown to be useful in the study of insulin binding and dissociation. Insulin binding to trypsinized platelets was considered to be nonspecific, since this fraction remained relatively constant during the incubation period at 25 C. Specific binding was evaluated by subtracting the nonspecific binding from the binding to untreated platelets; specific binding reached a plateau at 60 min. Scatchard analysis was conducted by adding increasing amounts of FITC-insulin to a platelet suspension. Furthermore, some of the prerequisites in analyzing insulin-receptor interaction were examined by this method.