Proteases and proteinase inhibitors in experimental glucocorticosteroid myopathy.

I Sohár, I Nagy, L Heiner, Z Kovács, F Guba
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Abstract

The unknown enzymatic mechanism of enhanced protein breakdown in steroid myopathy was studied in functionally and biochemically different muscles of rabbits treated with dexamethasone for three weeks. After glucocorticoid administration the fast-twitch glycolytic semimembraneous muscle of treated animals was atrophied, whereas the weight of the slow-twitch oxidative soleus muscle was not altered. The specific activity of the lysosomal endo- and exopeptidases (cathepsin D, E, B and L, lysosomal carboxypeptidase A and dipeptidylpeptidase I) was increased about 2-fold in the atrophied white muscle. The activity of the cytosol enzyme Ca++-activated neutral proteinase was also elevated, whereas that of the other cytosol endopeptidase, chymotrypsin-like enzyme, was unaltered. The level of alanine aminopeptidase was only slightly increased. On the other hand, there were no unequivocal changes in protease activity in the soleus muscle. These findings are in agreement with the known differences in glucocorticoid-sensitivity of the various muscles. Our results suggest that the lysosomal proteolytic system and the Ca++-activated neutral proteinase may play an important role in the glucocorticoid-induced intracellular protein catabolism in muscle. The inhibitor capacities of cathepsin B and trypsin detectable in muscle cytosol were not altered after steroid treatment. Consequently, the increase in cathepsin B activity was not due to the loss of its inhibitor.

实验性糖皮质激素性肌病的蛋白酶和蛋白酶抑制剂。
在地塞米松治疗三周的兔的功能和生化不同肌肉中,研究了类固醇肌病中蛋白质分解增强的未知酶机制。糖皮质激素给药后,治疗动物的快速收缩糖酵解半膜肌萎缩,而缓慢收缩氧化比目鱼肌的重量没有改变。萎缩白肌溶酶体内肽酶和外肽酶(组织蛋白酶D、E、B和L,溶酶体羧肽酶A和二肽基肽酶I)的比活性增加约2倍。细胞质酶ca++活化的中性蛋白酶活性也升高,而细胞质内肽酶乳糜蛋白酶样酶的活性则没有变化。丙氨酸氨基肽酶水平仅轻微升高。另一方面,比目鱼肌的蛋白酶活性没有明显的变化。这些发现与已知的不同肌肉对糖皮质激素敏感性的差异是一致的。我们的研究结果表明,溶酶体蛋白水解系统和ca++活化的中性蛋白酶可能在糖皮质激素诱导的肌肉细胞内蛋白分解代谢中起重要作用。在类固醇治疗后,肌细胞质中检测到的组织蛋白酶B和胰蛋白酶的抑制能力没有改变。因此,组织蛋白酶B活性的增加不是由于其抑制剂的丧失。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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