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Davis 2021 Comparative Exercise Physiology

From Bioblast
Publications in the MiPMap
Davis Michael, Barrett Montana, Popken Andrea (2021) Effect of hyperthermia and acidosis on equine skeletal muscle mitochondrial oxygen consumption. Comparative Exercise Physiology 17:171-179.


Davis Michael, Barrett Montana, Popken Andrea (2021) Comparative Exercise Physiology

Abstract: The skeletal muscle of exercising horses develops pronounced hyperthermia and acidosis during strenuous or prolonged exercise, with very high tissue temperature and low pH associated with muscle fatigue or damage. The purpose of this study was to evaluate the individual effects of physiologically relevant hyperthermia and acidosis on equine skeletal muscle mitochondrial function, using ex vivo measurement of oxygen consumption to assess the function of different mitochondrial elements. Fresh triceps muscle biopsies from 6 healthy unfit Thoroughbred geldings were permeabilised to permit diffusion of small molecular weight substrates through the sarcolemma and analysed in a high resolution respirometer at 38, 40, 42, and 44 °C, and pH=7.1, 6.5, and 6.1. Oxygen consumption was measured under conditions of non-phosphorylating (leak) respiration and phosphorylating respiration through Complex I and Complex II. Data were analysed using a one-way repeated measures ANOVA and data are expressed as mean ± standard deviation. Leak respiration was ~3-fold higher at 44 °C compared to 38 °C regardless of electron source (Complex I: 22.88±3.05 vs 8.08±1.92 pmol O2/mg/s), P=0.002; Complex II: 79.14±23.72 vs 21.43±11.08 pmol O2/mg/s, P=0.022), resulting in a decrease in efficiency of oxidative phosphorylation. Acidosis had minimal effect on mitochondrial respiration at pH=6.5, but pH=6.1 resulted in a 50% decrease in mitochondrial oxygen consumption. These results suggest that skeletal muscle hyperthermia decreases the efficiency of oxidative phosphorylation through increased leak respiration, thus providing a specific biochemical basis for hyperthermia-induced muscle fatigue. The effect of myocellular acidosis on mitochondrial respiration was minimal under typical levels of acidosis, but atypically severe acidosis can lead to impairment of mitochondrial function. Keywords: Horse, hyperthermia, lactic acid

O2k-Network Lab: US OK Stillwater Davis MS

Labels: MiParea: Exercise physiology;nutrition;life style 

Stress:Temperature  Organism: Horse  Tissue;cell: Skeletal muscle  Preparation: Permeabilized cells 

Regulation: Coupling efficiency;uncoupling, Temperature  Coupling state: LEAK, OXPHOS, ET  Pathway: N, S, NS  HRR: Oxygraph-2k