Fig. 5.

Presence of oxidized proteins in the cell activates several degradative machinery, release of aromatic amino acids after degradation, and elevation of intracellular [Ca²⁺]i in muscle. a The 20S proteasome activity was analyzed by using fluorogenic substrate Succ-LLVY-AMC. b Calcium ion-dependent calpain activity was also analyzed fluorometrically by using substrate SLY-AMC. c, d Hypobaric hypoxia causes elevation of release of aromatic amino acids tyrosine and tryptophan residues after the degradation through proteasome and calpain activity. e Resting intracellular [Ca²⁺]i in muscle. Data represents the mean ± SE; N = 5. Different symbols, double dagger, asterisk, and dagger indicate the significant differences between experimental groups (p < 0.05), while groups with matching symbols denote no difference (p ≥ 0.05)