Different sites of adenosine formation in the heart.
Different sites of adenosine formation in the heart.
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心脏中腺苷形成的不同部位。
DOI：
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发表时间：
1981
影响因子：
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通讯作者：
Eckehart Gerlach
中科院分区：
文献类型：
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作者：
W. Schutz;Jürgen Schrader;Eckehart Gerlach
为了进一步确定心肌腺苷形成的位置，我们在离体豚鼠心脏中灌注了5′-核苷酸酶[α， β -亚甲基腺苷5′-二磷酸（AOPCP）]和核苷转运[4-硝基苄基硫代肌苷（NBMPR）]的有效抑制剂。AOPCP （50 μ m）抑制心脏外泌5′-核苷酸酶活性85%，但不影响心脏在缺氧灌注（30% O2）时加速形成的腺苷、肌苷和次黄嘌呤的释放。相反，NBMPR（5微米）减少了缺氧诱导的腺苷及其降解物的释放，并大大增强了心肌组织中嘌呤化合物水平的增加。用5'-脱氧腺苷（一种不被代谢的腺苷衍生物）进行的研究表明，NBMPR可以抑制离体心脏和人红细胞中腺苷的摄取和释放。对豚鼠心室肌的细胞分离研究表明，5′-核苷酸酶虽然主要与膜部分相关，但也存在于心脏细胞质（200000 -g上清）中，表现出不同的底物特异性。此外，s -腺苷型同型半胱氨酸水解酶以及腺苷激酶和腺苷脱氨酶被证明只存在于细胞质部分。我们的研究结果表明，在缺氧的心脏中，a)外排5′-核苷酸酶很可能不参与腺苷的形成，b)从心脏释放腺苷需要腺苷通过肌膜运输，c)腺苷主要在细胞内形成，这一过程涉及胞质5′-核苷酸酶和/或s -腺苷同型半胱氨酸水解酶。
In an attempt to further define the site of myocardial adenosine formation, isolated guinea pig hearts were perfused with potent inhibitors of 5'-nucleotidase [alpha, beta-methylene adenosine 5'-diphosphate (AOPCP)] and of nucleoside transport [4-nitrobenzyl thioinosine (NBMPR)]. AOPCP (50 microM) inhibited the activity of cardiac ecto-5'-nucleotidase by 85% but did not influence the release of adenosine, inosine, and hypoxanthine formed at an accelerated rate by the heart during hypoxic perfusion (30% O2). In contrast, NBMPR (5 microM) diminished the hypoxia-induced release of adenosine and its degradatives and greatly potentiated the increase of myocardial tissue levels of respective purine compounds. Studies carried out with 5'-deoxyadenosine, an adenosine derivative that is not metabolized, indicate NBMPR to inhibit both uptake and release of adenosine in the isolated heart and in human erythrocytes. Cell fractionation studies on guinea pig ventricular muscle revealed that 5'-nucleotidase, though mainly associated with the membrane fraction, is also found in the cardiac cytosol (200,000-g supernatant), exhibiting a different substrate specificity. Furthermore, S-adenosylhomocysteine hydrolase as well as adenosine kinase and adenosine deaminase proved to be exclusively present in the cytosolic fraction. Our findings suggest that in the hypoxic heart a) ecto-5'-nucleotidase most likely is not involved in the formation of adenosine, b) release of adenosine from the heart requires adenosine to be transported across the sarcolemma membrane, and c) adenosine is predominantly formed intracellularly, a process involving cytosolic 5'-nucleotidase and/or S-adenosylhomocysteine hydrolase.