Organ uptake of 125I-hydroxybenzylpindolol, a potent beta adrenergic antagonist, was determined after intravenous administration. Pretreatment with the beta agonist, epinephrine, inhibited an almost identical fraction of 125I-hydroxybenzylpindolol binding as did the antagonist, propranolol. Specific beta receptor binding accounted for 50% of total uptake in the lung and demonstrated the following characteristics. The dose-response curve for propranolol inhibition of 125I-hydroxybenzylpindolol binding duplicated that reported for its physiologic action. Simultaneous serum propranolol levels as determined by a sensitive radioimmunoassay allowed an apparent dissociation rate constant approximately 7 nM to be obtained that correlated closely with the results reported from membrane binding studies. Alpha blockade had no effect and inhibition of 125I-hydroxybenzylpindolol binding by propranolol demonstrated stereospecificity. After chemical sympathectomy with reserpine or 6-OH dopamine, there was a 100% increase in receptor specific binding. Finally, a scintillation camera was employed to visually and quantitatively detect 125I-hydroxybenzylpindolol displacement from the lung during intravenous propranolol administration in the livin...Continue Reading
Adrenergic receptor trafficking is an active physiological process where adrenergic receptors are relocated from one region of the cell to another or from one type of cell to another. Discover the latest research on adrenergic receptor trafficking here.