Scholnick D A, Weinstein R B, Gleeson T T
University of Colorado, Department of Environmental Population and Organismic Biology, Boulder 80309-0334, USA.
Gen Comp Endocrinol. 1997 May;106(2):147-54. doi: 10.1006/gcen.1996.6866.
The skeletal muscles of ectothermic vertebrates possess an elevated glyconeogenic capacity that is responsible for a major portion of lactate removal and glycogen resynthesis following exercise. In lizards, changes in plasma hormone levels and the influence of differing hormone levels on muscle metabolism postexercise are poorly understood. We measured the effects of 5 min of exhaustive exercise on plasma levels of glucagon and corticosterone in the desert iguana Dipsosaurus dorsalis. We also determined the extent to which these hormones influence, or are influenced by, postexercise plasma lactate concentrations postexercise. Exercise resulted in the accumulation of 20 mM blood lactate, while plasma glucose levels remained stable throughout 90 min of recovery. Plasma glucagon was elevated sevenfold during 5 min of exercise and returned to resting levels within 45 min of recovery. Glucagon stimulated lactate incorporation into glycogen in isolated red muscle fiber bundles. Plasma corticosterone was also elevated to three times normal resting values, but only after 45 min of recovery. Blocking corticosterone elevation with metyrapone did not alter the kinetics of plasma lactate removal. In lizards, the dramatic rise in plasma glucagon occurs at the same time as previously reported elevated skeletal muscle glyconeogenesis and elevated glucagon stimulates lactate removal in vitro, strongly suggesting a role for glucagon in postexercise skeletal muscle metabolism.
变温脊椎动物的骨骼肌具有较高的糖异生能力，这在运动后乳酸清除和糖原再合成中占主要部分。在蜥蜴中，血浆激素水平的变化以及不同激素水平对运动后肌肉代谢的影响尚不清楚。我们测量了5分钟力竭运动对沙漠鬣蜥背纹双领蜥血浆胰高血糖素和皮质酮水平的影响。我们还确定了这些激素在运动后对血浆乳酸浓度的影响程度，或者受运动后血浆乳酸浓度影响的程度。运动导致血液中积累了20 mM的乳酸，而在90分钟的恢复过程中血浆葡萄糖水平保持稳定。运动5分钟期间，血浆胰高血糖素升高了7倍，并在恢复45分钟内恢复到静息水平。胰高血糖素刺激分离的红色肌纤维束中的乳酸掺入糖原。血浆皮质酮也升高到正常静息值的三倍，但仅在恢复45分钟后出现。用甲吡酮阻断皮质酮升高并没有改变血浆乳酸清除的动力学。在蜥蜴中，血浆胰高血糖素的急剧升高与先前报道的骨骼肌糖异生增加同时发生，并且胰高血糖素在体外刺激乳酸清除，强烈表明胰高血糖素在运动后骨骼肌代谢中起作用。
