Oxidant production and immune response after stretch injury in skeletal muscle

Purpose: This Study investigated oxidant production and associated immune r esponse after acute muscle stretch injury, Methods: A standardized single s tretch injury was performed on the tibialis anterior (TA) muscle of 36 male New Zealand white rabbits while contralateral control limbs underwent a sh am surgery. Animals were sacrificed 0, 4, 12, 24, 48, and 72 h after injury . Potential sites of oxidant production, measured with a dichlorofluorescei n (DCF) probe. were evaluated using two separate buffers. Results: Nonmitoc hondrial oxidant production measured under basal buffer conditions (0.1 M p otassium phosphate) Aas increased in both injured and control limbs at 24 h (P < 0.01) and was greater in the injured limb at 12 and 48 h (P < 0.01). There was also an interaction of time and injury (P < 0.05). Maximum oxidan t production by neutrophils and macrophages, stimulated by the induced buff er (including 1.7 mM ADP, 0.1 mM NADPH, 0.1 mM FeCl3). was increased in bot h injured and control limbs at 4 h (P < 0.01) and was greater in the injure d limb at 48 h (P < 0.01). Myeloperoxidase (MPO) activity. indicating the p resence of activated neutrophils, wa higher in the injured limb at 4 and 48 In (P < 0.01). The activities of superoxide radical producing and quenchin g enzymes. xanthine oxidase (XO) and Superoxide dismutase (SOD), were eleva ted at 24 (P < 0.01) and 4 h (P < 0.05). respectively. but showed no differ ence between injured and control limbs. Conclusion: we conclude that acute muscle stretch injury and the required surgeries to generate the injury res ult in a biphasic increase in oxidant production in both injured and contro l limbs, suggesting a systemic immune response, The increase in oxidant pro duction Lit 4 h may be caused by an increase in activated neutrophils. A wh ereas XO activity may contribute to oxidant generation at 24 h.