Photoaffinity labeling of the beta-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 1-isoprenaline and 2-(2-hydroxy-3-isopropylaminopropoxy)iodobenzene. The photoinactivation was eliminated in the presence of protectors of the receptors. Photoinactivation caused a considerable parallel shift in the concentration-action curve of 1-isoprenaline. The results possibly point to a certain receptor reserve for 1-isoprenaline.