Involvement of the oxygen storage protein myoglobin in muscle damage under oxidative stress

Myoglobin (Mb), the muscular oxygen reservoir, was shown to possess peroxidative reactivity in presence of H₂O₂ leading to oxidation of isolated cellular proteins like myosin. The objective of this study was to investigate the peroxidative effect of Mb/H₂O₂ on proteins in intact myofibrils (MF). Incubation of chicken leg MF in isotonic, pH 7.3 buffer at 37°C in the presence of Mb (30μM) and H₂O₂ (200μM), resulted in aggregation of MF material as inspected under light microscope. SDS-PAGE analysis revealed presence of high molecular weight aggregates at the expense of myosin heavy chains, but not actin. This crosslinking was unaffected by S- S reducing agents. Continuous low flow (0.03-3.00 μM/minute), produced by glucose oxidase and glucose, was more active than bolus H₂O₂ addition in myosin crosslinking in MF material. Hemin which may be released from Mb under oxidative stress, was more active than Mb as a trigger of MF peroxidative aggregation. Calcium-ATPase activity of crosslinked MF was considerably lost. These findings suggest that Mb/H₂O₂ may lead to oxidation of neighbouring muscular protein thereby jeopardize their functioning thus explaining muscular malfunction under oxidative stress.