Evidence for two atypical conformations of beta-adrenoceptors and their interaction with Gi proteins.

In this study, we investigated whether the responses of right atria from sinoaortic denervated rats to CGP12177 (4(3-t-butylamino-2-hydroxypropoxy benzidimidazole-2 one, hydrochloride)), isoprenaline and norepinephrine desensitized in parallel and whether CGP12177 interacted with distinct conformations of beta-adrenoceptors. Right atria from rats 48 h after sinoaortic denervation were subsensitive to isoprenaline, norepinephrine and CGP12177. One week after sinoaortic denervation, the sensitivity to CGP12177 had recovered whereas the responses to isoprenaline and norepinephrine were still subsensitive, suggesting that the binding sites for these molecules showed independent behavior.