Intracellular signalling pathway involved in ATP release from isolated smooth muscle cells.

在最近的研究中，已知ATP通过P2X和p2y嘌呤受体的激活表现出多种细胞反应，因此，似乎发挥了将信号传递到“细胞到细胞”的介质作用。在我们的一系列研究中，已经发现用去甲肾上腺素和乙酰胆碱刺激递质受体可引起平滑肌节段释放ATP。在项目第一年（1995年），用荧光素酶法测定了培养的豚鼠回肠和大肠带绦虫平滑肌细胞向过清液释放的ATP。ATP的释放在α、β -亚甲基ATP、乙二酚和血管紧张素II等多肽的存在下增加。增加的释放被各自的拮抗剂减弱。因此，研究结果表明ATP的释放来自平滑肌细胞。1996年，本研究集中于测定回肠纵肌匀浆在α， β -亚甲基ATP存在和不存在情况下肌醇1,4,5-三磷酸（IP3）的积累。IP3采用放射受体测定试剂盒（Amersham, TRK 1000）测定。p2激动剂增强了匀浆中IP3的积累。新霉素和Li^+分别阻断磷脂酶C和磷酸肌肽的转化，可以抑制这种增强的积累。由α、β -亚甲基ATP引起的ATP释放对百日咳毒素不敏感，并被新霉素、精胺和Li^+抵消。综上所述，IP3积累的增强可能与ATP的释放有关。

In recent investigations, ATP is known to exhibit a wide-variety of cell responses mediated by activation of P2X and P2Y-purinoceptors and, thus, seems to play roles of mediators to transfer signals to "cell to cell".In a series of our studies, it has been persented findings that stimulation of transmitters' receptors with noradrenaline and ACh elicits ATP release from smooth muscle segments.During the first year (1995) of the project, ATP released to superfusate from cultured smooth muscle cells from ileum and taenia coli of guinea-pig was measured by the luciferase method. The release of ATP was increased in the presence of alpha, beta-methylene ATP,bethanechol and peptides such as angiotensin II.The increased release was attenuated by respective antagonists. Accordingly, the findings suggest that ATP release comes from the smooth muscle cells.In 1996, the research project was focused on determination of inositol 1,4,5-trisphosphate (IP3) accumulation from the homogenate of ileal longitudinal muscles in the persence and absence of alpha, beta-methylene ATP.IP3 was measured by a radio-receptor assay using a IP3 assay kit (Amersham, TRK 1000). The P2-agonist enhanced the accumulation of IP3 in the homogenate. The enhanced accumulation was inhibited by blockade of phospholipase C and phosphoinositide turnover with neomycin and Li^+, respectively. The release of ATP evoked by alpha, beta-methylene ATP was insensitive to pertussis toxin and was counteracted by neomycin and spermine and by Li^+.Taken together, it is concluded that the enhancement of IP3 accumulation may be involved in the evoked release of ATP.