van der Ploeg I, Ahlberg S, Parkinson F E, Olsson R A, Fredholm B B
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Naunyn Schmiedebergs Arch Pharmacol. 1996 Feb;353(3):250-60. doi: 10.1007/BF00168626.
The effect of several adenosine analogues on cyclic AMP accumulation was examined in the rat phaeochromocytoma cell PC12 and in the human T-cell leukaemia cell Jurkat, selected as prototypes of cells predominantly expressing adenosine A2A or A2B receptors. Using the reverse transcription-polymerase chain reaction it was, however, demonstrated that the Jurkat cell and the PC12 cell express both A2A and A2B receptor mRNA, albeit in different relative proportions. In PC12 cells the concentration required for half-maximal response (EC50) for the full agonist 5'-N-ethyl-carboxamidoadenosine (NECA) was 30 times lower than in Jurkat cells. There was no significant difference in the pA2 for the antagonist 5-amino-9-chloro-2-(2-furanyl)- 1,2,4-triazolo(1,5-C)quinazolinemonomethanesulphonate (CGS 15943) between the two cell types. In the presence of forskolin (1 microM in PC12 cells; 10 microM in Jurkat cells) the EC50 value for NECA was reduced two-to sixfold. Forskolin also increased the maximal cAMP accumulation twofold in PC12 cells and sevenfold in Jurkat cells. A series of 2-substituted adenosine analogues CV 1808 (2-phenylamino adenosine), CV 1674 [2-(4-methoxyphenyl)adenosine], CGS 21680 ¿2-[p-(2-carbonylethyl)phenylethylamino]-5'-N-ethyl- carboxamido adenosine¿, and four 2-substituted isoguanosines, SHA 40 [2-(2-phenylethoxy)adenosine; PEA], SHA 91 [2-(2-cyclohexylethoxy)adenosine; CEA], SHA 118 ¿2-[2-(p-methylphenyl)ethoxy]adenosine; MPEA¿, and SHA 125 (2-hexyloxyadenosine; HOA), all raised cAMP accumulation in PC12 cells, but had minimal or no effect in Jurkat cells. In the PC12 cells the addition of forskolin (1 microM) reduced the EC50 by a factor of 2(CV 1808) to 12 (SHA 125). In Jurkat cells all the analogues gave a significant, but submaximal, cAMP response in the presence of forskolin (10 microM), but they were essentially inactive in its absence. The results show that a series of 2-substituted adenosine analogues can be used to discriminate between A2A and A2B receptors. The two receptor subtypes appear to coexist, even in clonal cells selected for typical pharmacology. A2 receptor pharmacology can therefore be complex.
在大鼠嗜铬细胞瘤细胞PC12和人T细胞白血病细胞Jurkat中检测了几种腺苷类似物对环磷酸腺苷（cAMP）积累的影响，这两种细胞分别被选作主要表达腺苷A2A或A2B受体的细胞原型。然而，通过逆转录-聚合酶链反应证明，Jurkat细胞和PC12细胞均表达A2A和A2B受体mRNA，尽管其相对比例不同。在PC12细胞中，完全激动剂5'-N-乙基-羧基酰胺腺苷（NECA）产生半数最大反应所需的浓度（EC50）比Jurkat细胞低30倍。两种细胞类型之间，拮抗剂5-氨基-9-氯-2-（2-呋喃基）-1,2,4-三唑并[1,5-c]喹唑啉单甲磺酸盐（CGS 15943）的pA2没有显著差异。在存在福司可林的情况下（PC12细胞中为1μM；Jurkat细胞中为10μM），NECA的EC50值降低了2至6倍。福司可林还使PC12细胞中的最大cAMP积累增加了两倍，使Jurkat细胞中的最大cAMP积累增加了七倍。一系列2-取代的腺苷类似物CV 1808（2-苯氨基腺苷）、CV 1674 [2-（4-甲氧基苯基）腺苷]、CGS 21680 [2-对-（2-羰基乙基）苯乙基氨基]-5'-N-乙基-羧基酰胺腺苷]以及四种2-取代的异鸟苷，SHA 40 [2-（2-苯乙氧基）腺苷；PEA]、SHA 91 [2-（2-环己乙氧基）腺苷；CEA]、SHA 118 [2-（2-对甲苯基）乙氧基]腺苷；MPEA]和SHA 125（2-己氧基腺苷；HOA），均能提高PC12细胞中的cAMP积累，但对Jurkat细胞的影响很小或没有影响。在PC12细胞中加入福司可林（1μM）可使EC50降低2倍（CV 1808）至12倍（SHA 125）。在Jurkat细胞中，所有类似物在存在福司可林（10μM）时均产生显著但未达到最大值的cAMP反应，但在不存在福司可林时基本无活性。结果表明，一系列2-取代的腺苷类似物可用于区分A2A和A2B受体。即使在因典型药理学特性而选择的克隆细胞中，这两种受体亚型似乎也共存。因此，A2受体药理学可能很复杂。
