Characterization of pharmacological receptors.

The isolation of macromolecules that bind drugs and neurohumoral mediators at receptor sites will require analytical methods adequate to detect these substances in homogenates and crude mixtures. Although the binding of isotopically labeled agonists has been useful in a few instances, equilibrium binding studies of radioactive, lipophilic antagonists promises to be more useful with beta-adrenergic receptors. Alkylation by radioactive reagents that seek out specific receptors or specific functional groups on protein have been used in attempts to label other receptors. Conformationally directed labeling of receptor and receptor-related proteins by the latter group of alkylating agents has been used with receptors for cardiac glycosides and may be applicable to other systems.