Identification of P2-purinergic receptors

1) PC12嗜铬细胞瘤细胞具有P2受体，其与Ca2+内流和儿茶酚胺释放偶联。在腺苷酸环化酶激活剂福斯克林的存在下，ATP类似物如ATP和2-甲基硫ATP以浓度依赖的方式抑制环AMP的积累。百日咳毒素完全消除了碳乙醇的作用，但对ATP的作用没有影响。此外，我们发现在胞外刺激后，adp核糖基化因子从胞浆部分转移到膜上。一种新的ATP受体的克隆仍有待确定。2)一氧化氮（NO）调节神经递质的释放。以前我们报道过5-亚硝基半胱氨酸刺激体内和体外海马释放去甲肾上腺素。在PC12细胞中，s -亚硝基半胱氨酸确实抑制去甲肾上腺素的释放。其他NO化合物增加了循环GMP的积累，但没有作用。在用s -亚硝基半胱氨酸处理的PC12细胞中，atp刺激的通过Ca2+通道的Ca2+内流被抑制，尽管s -亚硝基半胱氨酸刺激细胞内咖啡因敏感的Ca2+池中的Ca2+动员。NO从Ca2+池中动员Ca2+不是一个充分的因素，其他刺激释放的因素可能受到负调控。3)已知脂多糖或细胞因子通过在大鼠胶质细胞中诱导NO合成酶（iNOS）的表达刺激亚硝酸盐的产生。内皮素的共同添加降低了刺激物对iNOS的表达和亚硝酸盐的积累。相比之下，内皮素或ATP预处理24 h可增强iNOS的表达。内皮素和ATP的刺激作用分别由ET-B和P2受体介导。蛋白激酶C抑制剂抑制内皮素和atp增强的iNOS表达。刺激ATP受体可诱导神经胶质细胞中核因子NFkB的激活。

1) PC12 pheochromocytoma cells have P2 receptors which are coupled to Ca2+influx and catecholamine release. In the presence of forskolin, an activator of adenylyl cyclase, ATP analogs such as ATP and 2-methylthio ATP inhibited cyclic AMP accumulation in a concentration-dependent manner. Treatment with pertussis toxin, which completely abolished the effect of carbachol, had no effect on the action of ATP.In addition, we found that ADP-ribosylation factors translocate to membranes from the cytosol fraction after exocytotic stimulation. The cloning of a new type of ATP receptor remains to be determined.2) Nitric oxide (NO) modulates the release of neurotransmitters. Previously we reported that 5-nitroso-cysteine stimulated noradrenaline release from hippocampus in vivo and in vitro. In PC12 cells, S-nitroso-cysteine did inhibit noradrenaline release. Other NO compounds, which increased cyclic GMP accumulation, had no effect. ATP-stimulated Ca2+ influx via Ca2+ channels was inhibited in PC12 cells treated with S-Nitroso-cysteine, although S-nitroso-cysteine stimulated Ca2+ mobilization from intracellular caffeine-sensitive Ca2+-pools. Ca2+ mobilization by NO from Ca2+ pools was not a sufficient factor, and other factors stimulating release may be regulated negatively.3) Lipopolysaccaride or cytokines are known to stimulate production of nitrite via expression of inducible NO synthase (iNOS) in rat glial cells. Co-addition of endothelin decreased iNOS expression and nitrite accumulation by stimulants. In contrast, pretreatment with endothelin or ATP for 24 h enhanced iNOS expression. The stimulatory effect by endothelin or ATP was mediated by ET-B or P2 receptors, respectively. A protein kinase C inhibitor suppressed endothelin- and ATP-enhanced iNOS expression. Stimulation of ATP receptors induced activation of a nuclear factor, NFkB in glial cells.