Talmadge R J, Silverman H
Department of Zoology and Physiology, Louisiana State University, Baton Rouge 70803.
J Appl Physiol (1985). 1991 Jul;71(1):182-91. doi: 10.1152/jappl.1991.71.1.182.
The chronically active (pseudomyotonic) gastrocnemius muscle in the C57B16J dy2J/dy2J mouse contains both elevated lactate and glycogen as well as fibers that have high amounts of glycogen and enhanced glyconeogenic activity. In the present study we analyze the activities of some key glyconeogenic enzymes to assess the causes of elevated muscle glycogen and to determine the pathway for glycogen synthesis from lactate. Glycogen synthase, malate dehydrogenase, phosphoenolpyruvate carboxykinase, and malic enzyme were all elevated in homogenates of the chronically active muscle. Activities of glycogen phosphorylase and fructose 1,6-bisphosphatase were decreased in whole muscle homogenates. Histochemistry demonstrated that the high-glycogen fibers were typically fast-twitch glycolytic fibers that had high glycogen synthase, glycogen phosphorylase, and malic enzyme activities. Malate dehydrogenase activity followed succinate dehydrogenase activity and did not correlate to high-glycogen fibers. Thus the high-glycogen fibers have an elevated enzymatic capacity for glycogen synthesis from lactate, and the pathway may involve use of the pyruvate kinase bypass enzymes.
C57B16J dy2J/dy2J小鼠中慢性活跃（假肌强直）的腓肠肌含有升高的乳酸和糖原，以及具有大量糖原和增强糖异生活性的纤维。在本研究中，我们分析了一些关键糖异生酶的活性，以评估肌肉糖原升高的原因，并确定从乳酸合成糖原的途径。糖原合酶、苹果酸脱氢酶、磷酸烯醇式丙酮酸羧激酶和苹果酸酶在慢性活跃肌肉的匀浆中均升高。在全肌肉匀浆中，糖原磷酸化酶和果糖1,6-二磷酸酶的活性降低。组织化学表明，高糖原纤维通常是快肌糖酵解纤维，具有高糖原合酶、糖原磷酸化酶和苹果酸酶活性。苹果酸脱氢酶活性跟随琥珀酸脱氢酶活性，与高糖原纤维无关。因此，高糖原纤维从乳酸合成糖原的酶促能力升高，该途径可能涉及丙酮酸激酶旁路酶的使用。
