Agostini B, De Martino L, Soltau B, Hasselbach W
Max-Planck-Institut für Medizinische Forschung, Heidelberg, Bundesrepublik Deutschland.
Z Naturforsch C J Biosci. 1991 Nov-Dec;46(11-12):1109-26. doi: 10.1515/znc-1991-11-1229.
Calcium transport of skeletal muscle sarcoplasmic reticulum was comparatively studied in hibernating and summer active European hamsters (Cricetus cricetus L.). Crude homogenates from psoas, soleus and mixed skeletal muscles were used. Protein yield was strongly reduced in the muscle homogenates of hibernating hamsters. The calcium concentration in the muscle of hibernating hamsters was increased to a much higher content than in the serum. In the same animals the maximal rate of calcium uptake and the calcium storing capacity of sarcoplasmic reticulum were augmented by 43% and respectively 17%. Kinetic experiments with various concentrations of free calcium revealed in the hibernating animals higher uptake rates and a lower apparent calcium affinity than in the summer active hamsters. Some shift of calcium uptake rate and calcium affinity similar to that of a fast-twitch muscle was also observed in winter active animals kept at 22 degrees C under natural photoperiod. By contrast, the activity of the calcium dependent ATPase was not increased, suggesting a tighter coupling during hibernation between calcium dependent ATP-hydrolysis and calcium transport. No seasonal difference was observed in the calcium release by KCl-caffeine from calcium loaded vesicles of sarcoplasmic reticulum. Proportion and size of fibre types were studied with cold cross sections from psoas and soleus muscles. An average atrophy of about 25% was found during hibernation in both muscles. Cytochemistry revealed, however, a different reduction of cross area between type-I- and type-II-fibres, which reaches values up to 46% in the type-II-fast-fibres of the slow soleus muscle. Electron microscopy did not show any definite change in the distribution and amount of sarcoplasmic reticulum. The results suggest that during hibernation a modulation in the properties of calcium transport ATPase of sarcoplasmic reticulum occurs to better support the calcium transport function at low temperatures, which in turn warrants the restoration of ion homeostasis in the course of the arousal.
对冬眠和夏季活跃的欧洲仓鼠（Cricetus cricetus L.）的骨骼肌肌浆网钙转运进行了比较研究。使用了来自腰大肌、比目鱼肌和混合骨骼肌的粗匀浆。冬眠仓鼠的肌肉匀浆中蛋白质产量大幅降低。冬眠仓鼠肌肉中的钙浓度升高，比血清中的含量高得多。在同一动物中，肌浆网的最大钙摄取率和钙储存能力分别提高了43%和17%。对不同游离钙浓度进行的动力学实验表明，冬眠动物的摄取率高于夏季活跃的仓鼠，且表观钙亲和力较低。在自然光照周期下饲养于22摄氏度的冬季活跃动物中，也观察到钙摄取率和钙亲和力的一些变化，类似于快肌的变化。相比之下，钙依赖性ATP酶的活性没有增加，这表明冬眠期间钙依赖性ATP水解与钙转运之间的偶联更紧密。从肌浆网的钙负载囊泡中用氯化钾-咖啡因释放钙时，未观察到季节性差异。用腰大肌和比目鱼肌的冷切片研究了纤维类型的比例和大小。在冬眠期间，发现这两块肌肉平均萎缩约25%。然而，细胞化学显示I型和II型纤维之间横截面积的减少不同，在慢比目鱼肌的II型快纤维中，横截面积减少高达46%。电子显微镜未显示肌浆网的分布和数量有任何明确变化。结果表明，在冬眠期间，肌浆网钙转运ATP酶的性质发生调节，以更好地支持低温下的钙转运功能，这反过来又保证了觉醒过程中离子稳态的恢复。
