Metabolic and functional consequences of cytosolic 5′-nucleotidase-IA overexpression in neonatal rat cardiomyocytes
Metabolic and functional consequences of cytosolic 5′-nucleotidase-IA overexpression in neonatal rat cardiomyocytes
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DOI：
10.1152/ajpheart.00053.2003
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发表时间：
2003-09-01
影响因子：
4.8
通讯作者：
Newby, AC
中科院分区：
文献类型：
--
作者：
Sala-Newby, GB;Freeman, NVE;Newby, AC
腺苷对心脏发挥一系列能量保存作用，包括负变时作用。导致腺苷形成的途径仍然存在争议。特别是，尽管胞质 5'-核苷酸酶可以催化心肌细胞中腺苷的形成，但它们对腺苷作用的贡献先前尚未被记录。我们最近克隆了两种密切相关的 AMP 偏好胞质 5'-核苷酸酶（cN-IA 和 -IB）； A形式在心中占主导地位。在这项研究中，我们使用腺病毒在新生大鼠心肌细胞中过表达鸽子 cN-IA。在腺苷代谢抑制剂不存在和存在的情况下，cN-IA 过表达增加了模拟缺氧和异丙肾上腺素引起的腺苷形成和释放到培养基中。腺苷释放不受外切 5'-核苷酸酶抑制剂 α,β-亚甲基-ADP 的影响，但受核苷转运蛋白双嘧达莫的影响。在过表达 cN-IA 的细胞中，异丙肾上腺素的正变时作用（130 +/- 3 与 100 +/- 4 次/分钟）受到抑制（107 +/- 3 与 94 +/- 3 次/分钟），并且通过添加腺苷受体拮抗剂 8-(对磺苯基)茶碱（120 +/- 3 与 90 +/- 90 +/-）可逆转这种情况。 4 次/分钟）。我们的结果表明，过表达的 cN-IA 在心肌细胞中具有足够的活性，可在其受体处产生生理有效浓度的腺苷。
Adenosine exerts a spectrum of energy-preserving actions on the heart including negative chronotropic effects. The pathways leading to adenosine formation have remained controversial. In particular, although cytosolic 5'-nucleotidases can catalyze adenosine formation in cardiomyocytes, their contribution to the actions of adenosine has not been documented previously. We recently cloned two closely related AMP-preferring cytosolic 5'-nucleotidases (cN-IA and -IB); the A form predominates in the heart. In this study, we overexpressed pigeon cN-IA in neonatal rat cardiomyocytes using an adenovirus. cN-IA overexpression increased adenosine formation and release into the medium caused by simulated hypoxia and by isoproterenol in the absence and presence of inhibitors of adenosine metabolism. Adenosine release was not affected by an ecto-5'-nucleotidase inhibitor, alpha,beta-methylene-ADP, but was affected by a nucleoside transporter, dipyridamole. The positive chronotropic effect of isoproterenol (130 +/- 3 vs. 100 +/- 4 beats/min) was inhibited (107 +/- 3 vs. 94 +/- 3 beats/min) in cells overexpressing cN-IA, and this was reversed by the addition of the adenosine receptor antagonist 8-(p-sulfophenyl)theophilline (120 +/- 3 vs. 90 +/- 4 beats/min). Our results demonstrate that overexpressed cN-IA can be sufficiently active in cardiomyocytes to generate physiologically effective concentrations of adenosine at its receptors.