Goldfarb A H, Bruno J F, Buckenmeyer P J
Department of Physical Education, University of North Carolina, Greensboro 27412.
J Appl Physiol (1985). 1989 Jan;66(1):190-4. doi: 10.1152/jappl.1989.66.1.190.
To gain further insights into the mechanisms regulating skeletal muscle glycogenolysis during exercise, glycogen, phosphorylase, and adenosine 3',5'-cyclic monophosphate (cAMP) were determined in fast-twitch white (FTW) and fast-twitch red (FTR) muscle from groups of rats that ran for 0, 5, 10, 15, or 30 min at either 15 or 30 m/min. Glycogen degradation demonstrated an intensity and duration response in both fiber types. cAMP increased in both fiber types by 5 min and remained elevated at all times measured. FTW muscle cAMP levels were independent of both intensity and duration of exercise. FTR muscle cAMP levels were higher from 10 to 30 min at the 30-m/min intensity compared with the 15-m/min intensity. The ratio of the activity of phosphorylase in the presence of 2 mM AMP X 100 (phosphorylase a%) remained elevated at 20-22% independent of intensity and duration in FTW muscle; however, phosphorylase a% demonstrated an intensity and duration effect in FTR muscle. Glycogenolytic rates decreased with time, even though both cAMP and phosphorylase a% remained elevated in both fiber types. These data suggest that cAMP and phosphorylase a activation can be maintained during exercise in skeletal muscle but indicate a dissociation of these factors from glycogenolysis.
为了进一步深入了解运动过程中调节骨骼肌糖原分解的机制，对以15或30米/分钟的速度奔跑0、5、10、15或30分钟的大鼠组的快肌白肌（FTW）和快肌红肌（FTR）中的糖原、磷酸化酶和3',5'-环磷酸腺苷（cAMP）进行了测定。糖原降解在两种纤维类型中均表现出强度和持续时间反应。两种纤维类型中的cAMP在5分钟时均升高，并在所有测量时间内保持升高。FTW肌中的cAMP水平与运动强度和持续时间均无关。在30米/分钟强度下，FTR肌中的cAMP水平在10至30分钟时比15米/分钟强度时更高。在2 mM AMP存在下磷酸化酶的活性比值×100（磷酸化酶a%）在FTW肌中保持在20 - 22%的升高水平，与强度和持续时间无关；然而，磷酸化酶a%在FTR肌中表现出强度和持续时间效应。尽管两种纤维类型中的cAMP和磷酸化酶a%均保持升高，但糖原分解速率随时间下降。这些数据表明，在骨骼肌运动过程中，cAMP和磷酸化酶a的激活可以维持，但表明这些因素与糖原分解存在解离。
