Horská A, Fishbein K W, Fleg J L, Spencer R G
Gerontology Research Center, National Institutes of Health, National Institute on Aging, Baltimore, Maryland 21224, USA.
Am J Physiol Endocrinol Metab. 2000 Aug;279(2):E333-9. doi: 10.1152/ajpendo.2000.279.2.E333.
Using (31)P magnetic resonance spectroscopy, creatine kinase (CK) reaction kinetics was assessed in the forearm flexor digitorum profundus muscle of healthy young (n = 11, age 34.7 +/- 5 yr) and older (n = 20, age 73.5 +/- 8 yr) subjects at rest, intermittent exercise at 20% maximum voluntary contraction (MVC), and 40% MVC. Exercise resulted in a significant increase in the average ratio of inorganic phosphate (P(i)) to phosphocreatine (PCr) from resting values of 0.073 +/- 0.031 (young) and 0.082 +/- 0.037 (older) to 0. 268 +/- 0.140 (young, P < 0.01) and 0.452 +/- 0.387 (older, P < 0. 01) at 40% MVC. At 40% MVC, intracellular pH decreased significantly, from resting values of 7.08 +/- 0.08 (young) and 7.08 +/- 0.11 (older) to 6.84 +/- 0.19 (young, P < 0.05) and to 6.75 +/- 0.25 (older, P < 0.05). Average values of the pseudo-first-order reaction rate k((PCr-->ATP)) at rest were 0.07 +/- 0.04 s(-1) in the young and 0.07 +/- 0.03 s(-1) in the older group. At both exercise levels, the reaction rate constant increased compared with the resting value, but only the difference between the resting value and the 20% MVC value, which showed an 86% higher reaction rate constant in both groups, reached statistical significance (P < 0.05). No difference in the reaction rate constant between the young and older groups was observed at either exercise level. As with k((PCr-->ATP)), the average phosphorus flux through the CK reaction increased during exercise at 20% MVC (P < 0.05 in the older group) but decreased toward resting values at 40% MVC in both groups. The data in our study suggest that normal aging does not significantly affect the metabolic processes associated with the CK reaction.
利用磷磁共振波谱技术，在静息状态、20%最大自主收缩（MVC）和40%MVC的间歇性运动下，对健康年轻受试者（n = 11，年龄34.7±5岁）和老年受试者（n = 20，年龄73.5±8岁）的前臂指深屈肌中的肌酸激酶（CK）反应动力学进行了评估。运动导致无机磷酸盐（P(i)）与磷酸肌酸（PCr）的平均比值从静息值显著增加，年轻组静息值为0.073±0.031，老年组为0.082±0.037，在40%MVC时分别增至0.268±0.140（年轻组，P < 0.01）和0.452±0.387（老年组，P < 0.01）。在40%MVC时，细胞内pH值显著下降，年轻组从静息值7.08±0.08降至6.84±0.19（P < 0.05），老年组从静息值7.08±0.11降至6.75±0.25（P < 0.05）。年轻组静息时伪一级反应速率k((PCr→ATP))的平均值为0.07±0.04 s(-1)，老年组为0.07±0.03 s(-1)。在两个运动水平下，反应速率常数均比静息值增加，但只有静息值与20%MVC值之间的差异具有统计学意义（P < 0.05），两组该差异均显示反应速率常数高出86%。在任一运动水平下，未观察到年轻组与老年组反应速率常数的差异。与k((PCr→ATP))一样，在20%MVC运动期间，通过CK反应的平均磷通量增加（老年组P < 0.05），但在40%MVC时两组均降至静息值。我们研究中的数据表明，正常衰老不会显著影响与CK反应相关的代谢过程。
