Zoref-Shani E, Kessler-Icekson G, Wasserman L, Sperling O
Biochim Biophys Acta. 1984 Jun 19;804(2):161-8. doi: 10.1016/0167-4889(84)90145-9.
Primary rat cardiomyocyte cultures were utilized as a model for the study of purine nucleotide metabolism in the heart muscle, especially in connection with the mechanisms operating for the conservation of adenine nucleotides. The cultures exhibited capacity to produce purine nucleotides from nonpurine molecules (de novo synthesis), as well as from preformed purines (salvage synthesis). The conversion of adenosine to AMP, catalyzed by adenosine kinase, appears to be the most important physiological salvage pathway of adenine nucleotide synthesis in the cardiomyocytes. The study of the metabolic fate of IMP formed from [14C]formate or [14C]hypoxanthine and that of AMP formed from [14C]adenine or [14C]adenosine revealed that in the cardiomyocyte the main flow in the nucleotide interconversion pathways is from IMP to AMP, whereas the flux from AMP to IMP appeared to be markedly slower. Following synthesis from labeled precursors by either de novo or salvage pathways, most of the radioactivity in purine nucleotides accumulated in adenine nucleotides, and only a small proportion of it resided in IMP. The results suggest that the main pathway of AMP degradation in the cardiomyocyte proceeds through adenosine rather than through IMP. About 90% of the total radioactivity in purines effluxed from the cells during de novo synthesis from [14C]formate or following prelabeling of adenine nucleotides with [14C]adenine were found to reside in hypoxanthine. The activities in cell extracts of AMP 5'-nucleotidase and IMP 5'-nucleotidase, which catalyze nucleotide degradation, and of AMP deaminase, a key enzyme in the purine nucleotide cycle, were low. The nucleotidase activity resembles, and that of the AMP deaminase contrasts the respective enzyme activities in extracts of cultured skeletal-muscle myotubes. The results indicate that in the cardiomyocyte, in contrast to the myotube, the main mechanism operating for conservation of nucleotides is prompt phosphorylation of AMP, rather than operation of the purine nucleotide cycle. The primary cardiomyocyte cultures are a plausible model for the study of purine nucleotide metabolism in the heart muscle.
原代大鼠心肌细胞培养物被用作研究心肌中嘌呤核苷酸代谢的模型，特别是与腺嘌呤核苷酸保存机制相关的研究。这些培养物表现出从非嘌呤分子（从头合成）以及预先形成的嘌呤（补救合成）产生嘌呤核苷酸的能力。由腺苷激酶催化的腺苷向AMP的转化似乎是心肌细胞中腺嘌呤核苷酸合成最重要的生理补救途径。对由[14C]甲酸或[14C]次黄嘌呤形成的IMP以及由[14C]腺嘌呤或[14C]腺苷形成的AMP的代谢命运研究表明，在心肌细胞中核苷酸相互转化途径的主要流向是从IMP到AMP，而从AMP到IMP的通量似乎明显较慢。通过从头或补救途径由标记前体合成后，嘌呤核苷酸中的大部分放射性积累在腺嘌呤核苷酸中，只有一小部分存在于IMP中。结果表明，心肌细胞中AMP降解的主要途径是通过腺苷而不是通过IMP。在从[14C]甲酸从头合成期间或用[14C]腺嘌呤对腺嘌呤核苷酸进行预标记后，从细胞中流出的嘌呤中约90%的总放射性存在于次黄嘌呤中。催化核苷酸降解的AMP 5'-核苷酸酶和IMP 5'-核苷酸酶以及嘌呤核苷酸循环中的关键酶AMP脱氨酶在细胞提取物中的活性较低。核苷酸酶活性与培养的骨骼肌肌管提取物中的相应酶活性相似，而AMP脱氨酶的活性则与之相反。结果表明，与肌管相比，在心肌细胞中，保存核苷酸的主要机制是AMP的快速磷酸化，而不是嘌呤核苷酸循环的运作。原代心肌细胞培养物是研究心肌中嘌呤核苷酸代谢的一个合理模型。
