Kusachi S, Thompson R D, Olsson R A
J Pharmacol Exp Ther. 1983 Nov;227(2):316-21.
Adenosine receptors on the surface of coronary myocytes initiate coronary relaxation, but events subsequent to receptor occupancy are uncertain. We assayed the coronary vasoactivity of receptor-selective adenosine analogs in open chest dogs to test the hypothesis that the coronary adenosine receptor is an adenylate cyclase stimulatory (Ra) receptor. The potency order was: ethyl adenosine-5'-uronamide greater than cyclopropyl adenosine-5'-uronamide greater than 2-chloroadenosine greater than N6-[R(-)-1-phenyl-2-propyl] adenosine (R-PIA) greater than N6-cyclohexyladenosine greater than adenosine greater than S-PIA. Such a hierarchy of activity resembles that of the Ra receptors of thyroid and aortic myocyte adenylate cyclases and of tracheal smooth muscle relaxation. The potency order R-PIA greater than adenosine and the stereoselective coronary vasoactivity of R-PIA suggest that the coronary receptor may be a hybrid receptor which contains the "N6 site" typical of inhibitory (Ri) receptors in addition to the "5'-uronamide site' which expresses Ra activity.
冠状心肌细胞表面的腺苷受体引发冠状动脉舒张，但受体被占据后的后续事件尚不确定。我们在开胸犬中测定了受体选择性腺苷类似物的冠状血管活性，以检验冠状动脉腺苷受体是一种腺苷酸环化酶刺激性（Ra）受体的假说。效价顺序为：乙基腺苷-5'-脲酰胺＞环丙基腺苷-5'-脲酰胺＞2-氯腺苷＞N6-[R(-)-1-苯基-2-丙基]腺苷（R-PIA）＞N6-环己基腺苷＞腺苷＞S-PIA。这样的活性层次类似于甲状腺和主动脉肌细胞腺苷酸环化酶以及气管平滑肌舒张的Ra受体的活性层次。R-PIA＞腺苷的效价顺序以及R-PIA的立体选择性冠状血管活性表明，冠状动脉受体可能是一种混合受体，除了表达Ra活性的“5'-脲酰胺位点”外，还含有抑制性（Ri）受体典型的“N6位点”。
