ATP-evoked increases in [Ca2+]i and peptide release from rat isolated neurohypophysial terminals via a P2x2 purinoceptor
ATP-evoked increases in [Ca2+]i and peptide release from rat isolated neurohypophysial terminals via a P2x2 purinoceptor
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DOI：
10.1111/j.1469-7793.1998.089bi.x
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发表时间：
1998-08-15
影响因子：
5.5
通讯作者：
Dayanithi, G
中科院分区：
文献类型：
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作者：
Troadec, JD;Thirion, S;Dayanithi, G
1.用Fura-2显像技术观察了外源性ATP对单个神经垂体末梢胞浆游离Ca ~（2+）浓度（[Ca ~（2+）]（i））的影响。用特异性放射免疫分析法研究了ATP刺激后血管加压素（AVP）和催产素（OT）的释放. ATP引起持续的[Ca ~（2+）]（i）增加，在1-100 μ M范围内呈剂量依赖性（EC_（50）= 4.8 μ M）。这种效应仅在40%的终端中观察到。有趣的是，ATP在相同的范围内（EC_（50）= 8.6 μ M），诱发AVP，但没有显着的OT，从这些终端的释放。苏拉明对ATP引起的[Ca ~（2+）]（i）升高和AVP释放均有高度可逆的抑制作用，提示P-2嘌呤能受体参与ATP诱导的反应。另一种P-2嘌呤受体拮抗剂吡哆醛-5-磷酸-6-偶氮苯基-2 '，4'-二磺酸（PPADS）可显著降低ATP诱导的[Ca ~（2+）]（i）反应。为了进一步表征受体，测试了不同的激动剂，具有以下功效：ATP = 2-甲硫基-ATP> ATP-γ-S > α，β-亚甲基-ATP > ADP。化合物腺苷、AMP、β、γ-亚甲基-ATP和UTP无效。ATP依赖性[Ca ~（2+）]（i）增加依赖于细胞外Ca ~（2+）浓度（[Ca ~（2+）]（o））。Mn ~（2+）的荧光猝灭实验表明，外加ATP可引起Mn ~（2+）的内流。ATP诱导的[Ca ~（2+）]（i）增加和AVP释放除了对Cd ~（2+）不敏感外，还独立于K ~+诱导的反应，并与K ~+诱导的反应相加。在Gd ~（3+）存在下，ATP诱导的[Ca ~（2+）]（i）增加被强烈地降低。这些结果表明，观察到的[Ca 2 +]（i）增加是由Ca 2+通过P-2X通道受体进入而不是通过电压依赖性Ca 2+通道引起的。7.我们建议，ATP，共同释放的神经肽，可以作为一个旁分泌自分泌信使，刺激，通过Ca 2+进入通过P-2X2受体，分泌AVP，特别是从神经垂体神经末梢。
1. The effect of externally applied ATP on cytosolic free Ca2+ concentration ([Ca2+](i)) was tested in single isolated rat neurohypophysial nerve terminals by fura-2 imaging. The release of vasopressin (AVP) and oxytocin (OT) upon ATP stimulation was also studied from a population of terminals using specific radioimmunoassays.2. ATP evoked a sustained [Ca2+](i) increase, which was dose dependent in the 1-100 mu M range (EC50 = 4.8 mu M). This effect was observed in only similar to 40% of the terminals.3. Interestingly, ATP, in the same range (EC50 = 8.6 mu M), evoked AVP, but no significant OT, release from these terminals.4. Both the [Ca2+](i) increase and AVP release induced by ATP were highly and reversibly inhibited by suramin, suggesting the involvement of a P-2 purinergic receptor in the ATP-induced responses. Pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), another P-2 purinergic receptor antagonist, strongly reduced the ATP-induced [Ca2+](i) response.5. To further characterize the receptor, different agonists were tested, with the following efficacy: ATP = 2-methylthio-ATP > ATP-gamma-S > alpha,beta-methylene-ATP > ADP. The compounds adenosine, AMP, beta,gamma-methylene-ATP and UTP were ineffective.6. The ATP-dependent [Ca2+](i) increase was dependent on extracellular Ca2+ concentration ([Ca2+](o)). Fluorescence-quenching experiments with Mn2+ showed that externally applied ATP triggered a Mn2+ influx. The ATP-induced [Ca2+](i) increase and AVP release were independent of and additive to a K+-induced response, in addition to being insensitive to Cd2+. The ATP-induced [Ca2+](i) increase was strongly reduced in the presence of Gd3+. These results suggest that the observed [Ca2+](i) increases were elicited by Ca2+ entry through a P-2X channel receptor rather than via a voltage-dependent Ca2+ channel.7. We propose that ATP, co-released with neuropeptides, could act as a paracrine-autocrine messenger, stimulating, via Ca2+ entry through a P-2X2 receptor, the secretion of AVP, in particular, from neurohypophysial nerve terminals.