Abstract
It is strongly suggested that the beta-adrenoceptors in the taenia from the guinea pig caecum were irreversibly inactivated byphotoaffmity labeling with l-isoprenaline, since the photoinactivation was eliminated in the presence of the protector (propranolol) of the receptors.
There is a considerable parallel shift in the concentration action curve of l-isoprenaline by photoinactivation. The results possibly point to a certain receptor reserve for l-isoprenaline. Furthermore, effects of Ca ions, Mg ions andsmooth muscle stimulants on the interaction of l-isoprenaline with the beta-adrenoceptors were examined. The stable and persistent receptor block produced by photoaffmity labeling has utilized for this purpose. Ca ions only are involved in the combination of l-isoprenaline with the beta-adrenoceptors. The combination of l-isoprenaline with the beta-adrenoceptors was prevented in the presence of a cholinergic stimulant or high concentrations of histamine.
