Myocytes oxygenation and high energy phosphate levels during hypoxia.
Myocytes oxygenation and high energy phosphate levels during hypoxia.
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DOI：
10.1371/journal.pone.0101317
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Zhang J
中科院分区：
文献类型：
--
作者：
Jameel MN;Hu Q;Zhang J
在心肌细胞培养实验中，降低环境氧水平已被用于检测对缺氧继发性应激的反应性。然而，这些研究都没有测量肌细胞的氧合水平，导致关于是否存在氧输送不足的模糊性。本研究检验了以下假设：在基础心肌工作状态下，将维持足够的心肌细胞氧合，直至达到极低的动脉pO 2水平。正常犬的心肌细胞pO 2值使用1H-波谱（MRS）从心肌脱氧肌红蛋白（Mb- δ）水平计算，并标准化为LAD完全闭塞后获得的Mb-δ。在方案1（n = 6）中，在吸入气体的氧分数（FIO 2）从40、21、15、10和5%依次降低期间测量Mb-δ，而在方案2（n = 10）中，在FIO 2为3%时测量Mb-δ。 方案3（n = 9）评价了长期暴露于5% FIO 2期间Mb-δ的时间过程。 用微球测量心肌血流量（MBF），用~（31）P-MRS测定高能磷酸盐（HEP）水平。随着FIO_2的逐渐减少，MVO_2逐渐增加，伴随着LV压力、心率和MBF的增加。在FIO 2值为21、15、10和5%时，Mb-δ不可检测。而3%的FIO 2或5%的FIO 2长期暴露可引起Mb-δ的进行性升高，并伴有PCr、ATP和PCr/ATP比值的降低以及无机磷的升高。PCr和ATP降低20%时的细胞内PO 2值分别约为7.4和1.9 mmHg。这些数据表明，在体内系统中，在广泛的FIO 2和动脉pO 2水平范围内，肌细胞pO 2值保持远高于细胞色素氧化酶的Km值，并且在5%FIO2时，氧可用性不会限制线粒体氧化磷酸化。
Decrease of ambient oxygen level has been used in myocytes culture experiments in examining the responsiveness to stress secondary to hypoxia. However, none of these studies measure the myocytes oxygenation levels resulting in ambiguity as to whether there is insufficient oxygen delivery. This study examined the hypothesis that at a basal myocardial work state, adequate myocyte oxygenation would be maintained until extremely low arterial pO2 levels were reached. Myocyte pO2 values in normal dogs were calculated from the myocardial deoxymyoglobin (Mb- δ) levels using 1H-spectroscopy (MRS) and were normalized to Mb-δ obtained after complete LAD occlusion. During Protocol 1 (n = 6), Mb-δ was measured during sequential reductions of the oxygen fraction of inspired gas (FIO2) from 40, 21, 15, 10, and 5%, while in protocol 2 (n = 10) Mb-δ was measured at FIO2 of 3%. Protocol 3 (n = 9) evaluated time course of Mb-δ during prolonged exposure to FIO2 of 5%. Myocardial blood flow (MBF) was measured with microspheres and high energy phosphate (HEP) levels were determined with 31P-MRS. MVO2 progressively increased in response to the progressive reduction of FIO2 that is accompanied by increased LV pressure, heart rate, and MBF. Mb-δ was undetectable during FIO2 values of 21, 15, 10, and 5%. However, FIO2 of 3% or prolonged exposure to FIO2 of 5% caused progressive increases of Mb-δ which were associated with decreases of PCr, ATP and the PCr/ATP ratio, as well as increases of inorganic phosphate. The intracellular PO2 values for 20% reductions of PCr and ATP were approximately 7.4 and 1.9 mmHg, respectively. These data demonstrate that in the in vivo system over a wide range of FIO2 and arterial pO2 levels, the myocyte pO2 values remain well above the Km value with respect to cytochrome oxidase, and oxygen availability does not limit mitochondrial oxidative phosphorylation at 5% FIO2.
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DOI：
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发表时间：
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影响因子：
2.6
作者：
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DOI：
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发表时间：
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影响因子：
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作者：
OPIE, LH
通讯作者：
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影响因子：
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