Photoaffinity labelling of the β-adrenergic receptors and receptor reserve for isoprenaline

The beta-adrenergic receptors in the taenia isolated from the guinea pig caecum were irreversibly inactivated by photoaffinity labeling with l-isoprenaline and 2-(2-hydroxy-3-isopropylaminopropoxy)iodobenzene. The photoinactivation was elimination in the presence of protectors of the receptors. Photoinactivation caused a considerable parallel shift in the concentration-action curve of l-isoprenaline. The results possibly point to a certain receptor reserve for l-isoprenaline.