Mitochondrial Respirometry in Skeletal Muscle of Exercising Eventing Horses Run to Exhaustion

Abstract

IntroductionMitochondria play a central role in energy metabolism during muscle contraction and in the balance of anaerobic and aerobic energy production. This study evaluated mitochondrial respirometry in skeletal muscle of eventing horses before and after an intense effort.MethodsFourteen Brazilian Sport Horses 4 to 6 years old performed an incremental velocity test on a high speed treadmill inclined to 3% and galloped at speeds up to 8 m/s until exhaustion. Biopsies from the gluteus medius muscle were obtained before and immediately after the end of the test. Mitochondrial respiration was assessed by O2K oxygraph of high resolution (Oroboros). The results were standardized by minute and per gram of wet weight of muscle and expressed as mean ± SD. Plasma lactate was measured using a spectrophotometer. Results were compared by paired t–test (P<0.05).ResultsThe maximal respiration value of mitochondria did not change in gluteus medius muscle of horses at exhaustion. However, there was an increase in stage 3 mitochondrial respiration with pyruvate/malate substrate, and also an increase of non‐mitochondrial respiration after exercise. Lactate values before and after exercise were 0.4 ± 0.1 mmol/L and 12.1 ± 4.6 mmol/L, respectively.ConclusionsThere is little change in mitochondrial respirometry in the gluteus medius muscle after intense exercise indicating predominantly anaerobic metabolism in the muscle of the eventing horses, as supported by the high plasma lactate concentrations after the test. The increase of oxidase reactions after intense exercise is related to an increase in non‐mitochondrial respiration.Ethical Animal ResearchAll procedures were approved by the Board of Ethical Research of Universidade Federal Rural do Rio de Janeiro: number 264/2012. Sources of funding: Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq; PRONEX and Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro – FAPERJ. Competing interests: none.