14 Systemic and local antioxidant status is unaffected by repeated gluteal muscle collections in mature sedentary horses

Repeated skeletal muscle tissue collections are routinely utilized in research settings to determine the effects of various interventions or stressors on the muscle tissue. However, there is limited data on the effects of these muscle collections on the animal, creating difficulty in delineating impacts of interventions from the physiological response to tissue collection. Twenty-five mature, sedentary, stock-type horses (8 geldings, 17 mares; mean ± SD 9.5 ± 3.5 y, 505 ± 52 kg) were used to test the hypothesis that repeated skeletal muscle collections would not impact systemic or local antioxidant status. Horses were stratified by age and sex and randomly assigned to one of 4 groups: gluteus medius samples collected at 1) 0 and 24 h (n = 7); 2) 0 and 6 h (n = 5); 3) 0, 6, and 12 h (n = 7); or 4) 0, 6, 12, and 24 h (n = 6) using a 14-gauge tissue collection needle inserted to a standardized depth of 5 cm. Before collection, the site was aseptically prepared. Approximately 500 mg of tissue was obtained per collection through repeated insertions of the collection needle into the same skin puncture but at different angles. Blood was collected via jugular venipuncture from all horses every 6 h for 72 h, starting 24 h before the first muscle collection and extending to 48 h post-initial muscle collection. Throughout the collection period, horses remained group housedon Bahiagrass pastures and were only brought up to stocks for tissue collections. Malondialdehyde concentrations in muscle and superoxide dismutase and glutathione peroxidase (GPx) activities in muscle and whole blood were quantified via colorimetry. Data were analyzed using linear models in SAS v.9.4 with time as a repeated measure and horse as the subject. Time and sex were included as fixed effects. For blood parameters, collection group and the time × group interaction were included as additional fixed effects. Whole blood GPx activity was greater in group 4 horses (0, 6, 12, and 24 h) than horses in groups 1 (0 and 24 h) or 2 (0 and 6 h; P ≤ 0.02) and greater in mares than geldings (P ≤ 0.001). There were no other differences in skeletal muscle or whole blood antioxidant activities or muscle malondialdehyde concentrations over time or between groups of horses. These results suggest that repeated muscle tissue collections do not significantly impact antioxidant status of unstressed mature horses. Importantly, these data support the utility of repeated skeletal muscle collections in future study designs aimed at determining impacts of an array of interventions on skeletal muscle antioxidant status.