Kemp G J, Sanderson A L, Thompson C H, Radda G K
MRC Biochemical and Clinical Magnetic Resonance Unit, Oxford Radcliffe Hospital, UK.
NMR Biomed. 1996 Sep;9(6):261-70. doi: 10.1002/(SICI)1099-1492(199609)9:6<261::AID-NBM430>3.0.CO;2-B.
31P magnetic resonance spectroscopy measurements of pH and the concentrations of orthophosphate and phosphocreatine were used to estimate rates of glycogenolytic and oxidative ATP synthesis in rat leg muscle during 6 min sciatic nerve stimulation at different rates (1-4 Hz). To study the regulation of glycogenolysis during exercise, the apparent 'glycogenolytic capacity' (L(MAX)) was calculated from glycogenolytic ATP synthesis rate and orthophosphate concentration as a measure of the Ca2+-dependent activation of glycogen phosphorylase. This was found to be proportional to the total ATP synthesis rate (F), and to decline with time; expressed relative to total ATP turnover rate as L(MAX)/F, its initial value was 2.9+/-0.6, declining with half-time 1.4+/-0.4 min. The apparent 'mitochondrial capacity' (Q(MAX)), calculated from oxidative ATP synthesis rate and [ADP], was independent of ATP turnover rate, but increased with half-time 0.8+/-0.1 min to 29+/-2 mmol kg(-1) min(-1): thus [ADP] was the predominant but not the only influence on oxidative ATP synthesis. Numerical simulation shows that time-dependent changes in L(MAX)/F exert a strong influence on pH and on the concentrations of phosphocreatine and ADP.
利用31P磁共振波谱法测量pH值以及正磷酸盐和磷酸肌酸的浓度，以估计大鼠腿部肌肉在不同频率（1 - 4Hz）的坐骨神经刺激6分钟期间糖原分解和氧化ATP合成的速率。为了研究运动期间糖原分解的调节，从糖原分解ATP合成速率和正磷酸盐浓度计算表观“糖原分解能力”（L(MAX)），作为糖原磷酸化酶钙依赖性激活的指标。发现其与总ATP合成速率（F）成正比，并随时间下降；相对于总ATP周转率表示为L(MAX)/F，其初始值为2.9±0.6，半衰期为1.4±0.4分钟时下降。由氧化ATP合成速率和[ADP]计算得出的表观“线粒体能力”（Q(MAX)）与ATP周转率无关，但以半衰期0.8±0.1分钟增加至29±2 mmol kg(-1) min(-1)：因此[ADP]是对氧化ATP合成的主要但非唯一影响因素。数值模拟表明，L(MAX)/F随时间的变化对pH值以及磷酸肌酸和ADP的浓度有很大影响。
