Larrouy D, Remaury A, Daviaud D, Lafontan M
INSERM U317, Institut Louis Bugnard, Université Paul Sabatier, CHU Rangueil, Toulouse, France.
Eur J Pharmacol. 1994 Apr 15;267(2):225-32. doi: 10.1016/0922-4106(94)90174-0.
Adenosine A1 receptors and alpha 2-adrenoceptors are both potent inhibitors of adipocyte lipolysis when activated by their agonists. The aim of this work was to compare the coupling of these receptors to the Gi-proteins in hamster adipocytes. The adenosine A1 receptor was characterized with the antagonist [3H]dipropyl-cyclopentyl-xanthine ([3H]DPCPX) and the agonist 3H-phenylisopropyladenosine ([3H]PIA). It was demonstrated by [32P]ADP-ribosylation with pertussis toxin and immunoblotting that Gi1, Gi2 and Gi3 are expressed in hamster adipocytes. Partial ADP-ribosylation of Gi-proteins by pertussis toxin, acting on the intact cells or on the adipocyte membranes, demonstrated that the adenosine A1 receptor was less sensitive to the disappearance of functional Gi-proteins than the alpha 2-adrenoceptor. These results are in accordance with the weak sensitivity of the binding of the agonist [3H]PIA to guanine nucleotides and seem to confirm that the adenosine A1 receptor is strongly and differently coupled than the alpha 2-adrenoceptor to the Gi-proteins in hamster adipocyte membranes.
腺苷A1受体和α2-肾上腺素能受体在被其激动剂激活时，都是脂肪细胞脂肪分解的有效抑制剂。本研究的目的是比较这些受体与仓鼠脂肪细胞中Gi蛋白的偶联情况。腺苷A1受体用拮抗剂[3H]二丙基-环戊基-黄嘌呤（[3H]DPCPX）和激动剂3H-苯异丙基腺苷（[3H]PIA）进行表征。通过百日咳毒素的[32P]ADP-核糖基化和免疫印迹证明，Gi1、Gi2和Gi3在仓鼠脂肪细胞中表达。百日咳毒素对完整细胞或脂肪细胞膜上的Gi蛋白进行部分ADP-核糖基化，结果表明，与α2-肾上腺素能受体相比，腺苷A1受体对功能性Gi蛋白消失的敏感性较低。这些结果与激动剂[3H]PIA与鸟嘌呤核苷酸结合的弱敏感性一致，似乎证实了在仓鼠脂肪细胞膜中，腺苷A1受体与α2-肾上腺素能受体与Gi蛋白的偶联强烈且不同。
