Arch Gerontol Geriatr. 1994;19 Suppl 1:123-8. doi: 10.1016/s0167-4943(05)80057-3.
Parvalbumin is a calcium-binding protein involved in the mechanism of Ca(++) exchange between the sarcoplasmic reticulum and the myofibrils. There is a direct correlation between the amount of parvalbumin and the velocity of contraction-relaxation of skeletal muscle fibers. Male Donryu rats (6, 24 and 30 months of age) were housed in a specific pathogen free room and fed with 60% of the mean daily quantity of rodent chow consumed by rats fed ad libitum. To assess the expression of parvalbumin in the rat diaphragm, transversal sections were processed immunohistochemically using polyclonal antiparvalbumin antibody. The stained sections were inspected on an image analysis device to evaluate the intensity of the immunoreaction and to take morphological measurements of the muscle fibers. The optical density data allowed the distinction of fibers in fast- and slow-twitch types. The results show that the number of fibers did not change in young and old rats, but the percentage of muscle fibers containing parvalbumin decreased with age. Moreover, the fast-twitch fibers showed a remarkable decrease in their diameter at 30 months of age, but the slow-twitch ones did not. The results suggest that, as the organism gets old, the fiber type composition of the diaphragm changes to adapt to different physiological and/or metabolic exigencies.
肌钙蛋白是一种钙结合蛋白，参与肌浆网和肌原纤维之间 Ca(++)交换的机制。肌钙蛋白的含量与骨骼肌纤维收缩-松弛的速度之间存在直接的相关性。雄性土龙（6、24 和 30 个月大）被安置在一个无特定病原体的房间中，并以 60%的自由进食大鼠每日平均食量喂养。为了评估肌钙蛋白在大鼠横膈膜中的表达，使用多克隆抗肌钙蛋白抗体对横切片进行免疫组织化学处理。用图像分析设备检查染色切片，以评估免疫反应的强度，并对肌肉纤维进行形态学测量。光密度数据允许区分快肌和慢肌纤维。结果表明，年轻和老年大鼠的纤维数量没有变化，但含有肌钙蛋白的肌肉纤维百分比随着年龄的增长而减少。此外，快肌纤维在 30 个月时其直径显著减小，但慢肌纤维则没有。结果表明，随着机体的衰老，横膈膜的纤维类型组成发生变化，以适应不同的生理和/或代谢需求。
