Gillis J M
Department of Physiology, Catholic University of Louvain, Bruxelles, Belgium.
Acta Physiol Scand. 1996 Mar;156(3):397-406. doi: 10.1046/j.1365-201X.1996.201000.x.
Muscles of the mdx mouse lack dystrophin, a cytoskeletal protein. Mdx fibres exhibit an increased fragility to hypo-osmotic shock and to forced lengthening, an abnormal opening time of stretch-sensitive calcium channels. The question of a chronic elevated [Ca2+]i value is a matter of controversy. We have analysed Ca homeostasis in smooth and skeletal muscles from the adult mdx mouse. The wall of the vas deferens was loaded with the fluorescent Ca indicator Fura-2-AM (cell-diffusible). Resting [Ca2+]i was measured after changes of the electrochemical potential for Ca2+ and after KCl or electrical stimulations. In no instance was a difference observed between these and similar muscles from control mice. Single striated fibres were isolated by collagenase treatment of the flexor digitorum brevis muscle and loaded with Fura-2-AM. The value of resting [Ca2+]i was measured using an in situ calibration procedure which took account of Ca buffering by Fura-2. A chronic increase of cytosolic Ca2+ was not confirmed. The expression of the intracellular Ca-binding protein, parvalbumin, was measured. It increased by about threefold in fast mdx muscles (tibialis anterior) but remained undetectable in the soleus. It is hypothesized that parvalbumin helps to maintain [Ca2+]i within normal values. This hypothesis will be discussed in connection with dystrophy phenotypes in mutant dogs and in human patients.
mdx小鼠的肌肉缺乏肌营养不良蛋白，一种细胞骨架蛋白。mdx肌纤维对低渗休克和强制拉长表现出更高的脆弱性，拉伸敏感钙通道的开放时间异常。关于细胞内钙离子浓度（[Ca2+]i）长期升高的问题存在争议。我们分析了成年mdx小鼠平滑肌和骨骼肌中的钙稳态。输精管壁用荧光钙指示剂Fura-2-AM（可细胞扩散）加载。在钙离子电化学势变化后以及氯化钾或电刺激后测量静息[Ca2+]i。在这些肌肉与对照小鼠的相似肌肉之间未观察到差异。通过胶原酶处理趾短屈肌分离出单个横纹肌纤维，并用Fura-2-AM加载。使用考虑了Fura-2对钙缓冲作用的原位校准程序测量静息[Ca2+]i值。未证实细胞溶质钙的慢性增加。测量了细胞内钙结合蛋白小白蛋白的表达。它在快速收缩的mdx肌肉（胫前肌）中增加了约三倍，但在比目鱼肌中仍未检测到。据推测，小白蛋白有助于将[Ca2+]i维持在正常范围内。将结合突变犬和人类患者的营养不良表型来讨论这一假设。
