The research study aimed to examine the effects on horses’ mitochondrial function, antioxidant status, and inflammation markers in response to repeated muscle biopsies. The primary findings indicate limited or no short-term effects on most physiological markers, barring the increase in serum creatine kinase activity.

Research Design and Methodology

• The study involved 26 horses – 8 geldings and 18 mares aged approximately 9.5 years. The gluteus medius muscle biopsy samples were collected at various time intervals. The participants were divided into four groups, differentiated by the time frames at which samples were collected.
• In addition to the muscle samples, blood was also collected from all horses every 6 hours for a total of 72 hours, starting 24 hours prior to the first muscle collection.
• The collected data was analyzed using mixed linear models.

Findings and Interpretation

• The results showed that within the initial 6 hours, the per mg tissue electron transfer capacity of complex II decreased, and intrinsic LEAK, relative to citrate synthase (CS) activity, increased. However, these measures returned to their initial levels by the 12-hour mark.
• CS activity was higher at initiation than at the 12-hour and 24-hour marks.
• Serum creatine kinase (CK) activity was consistent up to the biopsy’s commencement, increased in all horses at 6 hours, and maintained the elevated state till 48 hours. Despite this increase, CK levels remained within reference ranges, suggesting that though biopsies cause a CK activity increase, they do not push it beyond normal levels.
• There was no remarkable change in whole blood superoxide dismutase activity and serum cortisol concentration due to muscle collections, even though these displayed fluctuations and a circadian pattern respectively over the course of 72 hours.
• No other variables, including muscle mitochondrial capacities and function, blood and muscle antioxidant status and concentrations of selected cytokines, and serum amyloid A, differed by time or muscle collection. This indicates that repeated muscle collections do not have a substantive effect on these physiological markers.

Conclusion and Implications

• Overall, repeated muscle collections had limited short-term effects or none on the physiological markers in middle-aged, unstressed horses, except for an increase in serum CK activity.
• Such a result implies that while interpreting the results of repeated tissue collections in studies involving horses, the standard increase in serum CK activity should be taken into account.