Conley K E, Jubrias S A, Esselman P C
Department of Radiology, University of Washington Medical Center, Seattle, WA 98195-7115, USA.
J Physiol. 2000 Jul 1;526 Pt 1(Pt 1):203-10. doi: 10.1111/j.1469-7793.2000.t01-1-00203.x.
This study determined the decline in oxidative capacity per volume of human vastus lateralis muscle between nine adult (mean age 38.8 years) and 40 elderly (mean age 68.8 years) human subjects (age range 25-80 years). We based our oxidative capacity estimates on the kinetics of changes in creatine phosphate content ([PCr]) during recovery from exercise as measured by (31)P magnetic resonance (MR) spectroscopy. A matched muscle biopsy sample permitted determination of mitochondrial volume density and the contribution of the loss of mitochondrial content to the decline in oxidative capacity with age. The maximal oxidative phosphorylation rate or oxidative capacity was estimated from the PCr recovery rate constant (k(PCr)) and the [PCr] in accordance with a simple electrical circuit model of mitochondrial respiratory control. Oxidative capacity was 50 % lower in the elderly vs. the adult group (0.61 +/- 0.04 vs. 1.16 +/- 0.147 mM ATP s(-1)). Mitochondrial volume density was significantly lower in elderly compared with adult muscle (2.9 +/- 0.15 vs. 3.6 +/- 0.11 %). In addition, the oxidative capacity per mitochondrial volume (0.22 +/- 0.042 vs. 0.32 +/- 0.015 mM ATP (s %)(-1)) was reduced in elderly vs. adult subjects. This study showed that elderly subjects had nearly 50 % lower oxidative capacity per volume of muscle than adult subjects. The cellular basis of this drop was a reduction in mitochondrial content, as well as a lower oxidative capacity of the mitochondria with age.
本研究测定了9名成年人（平均年龄38.8岁）和40名老年人（平均年龄68.8岁）（年龄范围25 - 80岁）股外侧肌每单位体积氧化能力的下降情况。我们根据运动恢复过程中磷酸肌酸含量（[PCr]）变化的动力学来估算氧化能力，该变化通过（31）P磁共振（MR）波谱测定。匹配的肌肉活检样本有助于确定线粒体体积密度以及线粒体含量的损失对氧化能力随年龄下降的贡献。根据线粒体呼吸控制的简单电路模型，从磷酸肌酸恢复速率常数（k(PCr)）和[PCr]估算最大氧化磷酸化速率或氧化能力。与成年组相比，老年组的氧化能力降低了50%（0.61±0.04对1.16±0.147 mM ATP s(-1)）。与成年肌肉相比，老年肌肉中的线粒体体积密度显著降低（2.9±0.15对3.6±0.11%）。此外，与成年受试者相比，老年受试者每线粒体体积的氧化能力（0.22±0.042对0.32±0.015 mM ATP (s %)(-1)）也降低了。本研究表明，老年受试者每单位肌肉体积的氧化能力比成年受试者低近50%。这种下降的细胞基础是线粒体含量的减少以及随着年龄增长线粒体氧化能力的降低。
