A noninvasive assessment of pharmacological interaction of amines in the lung

Lung endothelial binding sites of N-isopropyl-123I-p-iodoamphetamine (123I-IMP) were assessed employing the principle of competitive binding assay adapted for in vivo measurement using a computer-scintillation camera technique. A noninvasive modification of the Chinard-Crone technique was applied to the study of pulmonary extraction. 123I-IMP, the test cellular tracer and 99Tcm-dextran the vascular reference tracer were used in dogs to determine the first pass pulmonary extraction of 123I-IMP. The lung extraction of 123I-IMP decreases progressively from 90 to 62% as the amount of propranolol (administered 10 min prior to the injection of 99Tcm-dextran) gradually increased from 0 to 20 mg. The dissociation constant of 123I-IMP lung binding sites reaction in the presence of propranolol was calculated by Scatchard plot and found to be 10 mg. The in vivo procedure described in this paper will enable us to develop a model for the assay of the binding sites in the lungs for amine and its influence in both health and disease.