Schütz W, Steurer G, Tuisl E
Eur J Pharmacol. 1982 Nov 19;85(2):177-84. doi: 10.1016/0014-2999(82)90463-0.
It was investigated whether adenosine affects the adenylate cyclase system of microvessels, isolated from the rat cerebral cortex, via an external receptor recently classified as R-site receptor. Several adenosine analogs caused GTP-dependent stimulation of adenylate cyclase. The rank order of potency: NECA (5'-(N-ethylcarboxamido)-adenosine, EC50 0.2 microM) greater than adenosine (0.71 microM) = 2-chloroadenosine (0.72 microM) greater than L-PIA (N6-(L-phenylisopropyl)-adenosine, 1.03 microM) greater than D-PIA (N6-(D-phenylisopropyl)-adenosine, 5.27 microM) is consistent with that for agonism at activatory (Ra-site) adenosine receptors in other tissues. Adenylate cyclase stimulation by PIA displayed stereoselectivity. The action of NECA was competitively antagonized by 8-phenyltheophylline. These findings provide functional evidence for Ra-site adenosine receptors in rat brain microvessels. However, direct identification of these receptors by binding studies was not possible. Binding of [3H]NECA to rat brain microvessels displayed rapid on-off kinetics and saturability, but equivocal specificity.
研究了腺苷是否通过最近归类为R位点受体的外部受体影响从大鼠大脑皮层分离的微血管的腺苷酸环化酶系统。几种腺苷类似物引起了GTP依赖性的腺苷酸环化酶刺激。效力顺序为：NECA（5'-（N-乙基羧酰胺基）-腺苷，EC50 0.2 microM）大于腺苷（0.71 microM）= 2-氯腺苷（0.72 microM）大于L-PIA（N6-（L-苯异丙基）-腺苷，1.03 microM）大于D-PIA（N6-（D-苯异丙基）-腺苷，5.27 microM），这与其他组织中激活型（Ra位点）腺苷受体的激动作用顺序一致。PIA对腺苷酸环化酶的刺激表现出立体选择性。NECA的作用被8-苯基茶碱竞争性拮抗。这些发现为大鼠脑微血管中的Ra位点腺苷受体提供了功能证据。然而，通过结合研究直接鉴定这些受体是不可能的。[3H]NECA与大鼠脑微血管的结合表现出快速的结合-解离动力学和饱和性，但特异性不明确。
