Rat cardiac myocyte adenosine transport and metabolism.
Rat cardiac myocyte adenosine transport and metabolism.
复制标题
大鼠心肌细胞腺苷转运和代谢。
DOI：
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发表时间：
1987
影响因子：
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通讯作者：
M. Rovetto
中科院分区：
文献类型：
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作者：
D. Ford;M. Rovetto
基于心肌腺苷和腺苷核苷酸代谢的重要性，研究了心室肌细胞的腺苷回收途径。确定了与代谢通量分离的运输速率的准确估计。腺苷内流在3到60秒之间是恒定的。腺苷代谢维持细胞内腺苷浓度低于细胞外腺苷浓度的10%，因此可以测量单向内流。肌细胞通过饱和(Michaelis常数= 6.2 +/- 2.1微米，最大速度（Vmax) = 9.58 +/- 0.98 X 10(-1) pmol X mg protein-1 X s-1）和非饱和（速率常数= 1.8 X 10(-3)/s）过程运输腺苷。肌细胞腺苷激酶Vmax （2 pmol X mg protein-1 X s-1）的最小估计表明，腺苷内流的可饱和成分与腺苷激酶活性无关。硝基苄基硫代肌苷和维拉帕米（抑制剂常数为17 +/- 5 μ m）可抑制饱和转运。肌细胞摄取的胞外腺苷被迅速磷酸化为腺嘌呤核苷酸。然而，并不是所有的细胞外腺苷在进入肌细胞时都被磷酸化，因为在1 mM乙二胺四乙酸存在的情况下，洋地黄苷提取细胞后检测到游离的细胞内腺苷，而不是蛋白质结合的腺苷。
Based on the importance of myocardial adenosine and adenine nucleotide metabolism, the adenosine salvage pathway in ventricular myocytes was studied. Accurate estimates of transport rates, separate from metabolic flux, were determined. Adenosine influx was constant between 3 and 60 s. Adenosine metabolism maintained intracellular adenosine concentrations less than 10% of the extracellular adenosine concentrations and thus unidirectional influx could be measured. Myocytes transported adenosine via saturable [Michaelis constant = 6.2 +/- 2.1 microM and maximal velocity (Vmax) = 9.58 +/- 0.98 X 10(-1) pmol X mg protein-1 X s-1] and nonsaturable (rate constant = 1.8 X 10(-3)/s) processes. A minimum estimate of the Vmax of myocytic adenosine kinase (2 pmol X mg protein-1 X s-1) indicated the saturable component of adenosine influx was independent of adenosine kinase activity. Saturable transport was inhibited by nitrobenzylthioinosine and verapamil (inhibitor constant = 17 +/- 5 microM). Extracellular adenosine taken up by myocytes was rapidly phosphorylated to adenine nucleotides. Not all extracellular adenosine, though, was phosphorylated on entering myocytes, since free, as opposed to protein-bound, intracellular adenosine was detected after digitonin extraction of cells in the presence of 1 mM ethylene-diaminetetraacetic acid.