Zhan W Z, Miyata H, Prakash Y S, Sieck G C
Department of Anesthesiology, Mayo Foundation, Rochester, Minnesota 55905, USA.
J Appl Physiol (1985). 1997 Apr;82(4):1145-53. doi: 10.1152/jappl.1997.82.4.1145.
We hypothesized that metabolic adaptations to muscle inactivity are most pronounced when neurotrophic influence is disrupted. In rat diaphragm muscle (Dia(m)), 2 wk of unilateral denervation or tetrodotoxin nerve blockade resulted in a reduction in succinate dehydrogenase (SDH) activity of type I, IIa, and IIx fibers (approximately 50, 70, and 24%, respectively) and a decrease in SDH variability among fibers (approximately 63%). In contrast, inactivity induced by spinal cord hemisection at C2 (ST) resulted in much less change in SDH activity of type I and IIa fibers (approximately 27 and 24%, respectively) and only an approximately 30% reduction in SDH variability among fibers. Actomyosin adenosinetriphosphatase (ATPase) activities of type I, IIx, and IIb fibers in denervated and tetrodotoxin-treated Dia(m) were reduced by approximately 20, 45, and 60%, respectively, and actomyosin ATPase variability among fibers was approximately 60% lower. In contrast, only actomyosin ATPase activity of type IIb fibers was reduced (approximately 20%) in ST Dia(m). These results suggest that disruption of neurotrophic influence has a greater impact on muscle fiber metabolic properties than inactivity per se.
我们推测，当神经营养影响被破坏时，对肌肉不活动的代谢适应最为明显。在大鼠膈肌（Dia(m)）中，2周的单侧去神经支配或河豚毒素神经阻滞导致I型、IIa型和IIx型纤维的琥珀酸脱氢酶（SDH）活性降低（分别约为50%、70%和24%），并且纤维间SDH变异性降低（约63%）。相比之下，C2水平脊髓半横断（ST）诱导的不活动导致I型和IIa型纤维的SDH活性变化小得多（分别约为27%和24%），纤维间SDH变异性仅降低约30%。去神经支配和经河豚毒素处理的Dia(m)中，I型、IIx型和IIb型纤维的肌动球蛋白腺苷三磷酸酶（ATPase）活性分别降低约20%、45%和60%，纤维间肌动球蛋白ATPase变异性降低约60%。相比之下，ST Dia(m)中仅IIb型纤维的肌动球蛋白ATPase活性降低（约20%）。这些结果表明，神经营养影响的破坏对肌纤维代谢特性的影响大于不活动本身。
