Effects of Hyperthermia and Acidosis on Mitochondrial Oxidative Phosphorylation.

This research article studies the impact of high temperature (hyperthermia) and high acidity (acidosis) inside muscle cells during intense exercise on ATP synthesis, the process by which our bodies produce energy. Using racehorses as their test subjects, the researchers hypothesise that both hyperthermia and acidosis disrupt ATP synthesis, but athletic conditioning can lessen this negative effect.

Objective and Methodology

• The study aims to understand the influence of hyperthermia and acidosis, conditions that typically develop in the muscular cells during strenuous exertion, on the generation of ATP (adenosine triphosphate), which is the main source of energy in cells.
• The researchers used Thoroughbred racehorses as subjects, taking isolated mitochondria – the energy-producing units in a cell – from the horse’s skeletal muscle before and after a 9-week racetrack conditioning program.
• The conditioning program was effective in increasing the horses’ whole-body aerobic capacity by 19%, thereby improving their overall fitness level.
• The harvested mitochondria were then subjected to both normal and hyperthermic (high-temperature) conditions as well as normal and acidic pH levels to test their ATP synthesis capabilities performed under these conditions.

Findings and Observations

• In horses that had not undergone the conditioning program, hyperthermia resulted in a 30-55% reduction in ATP synthesis and decreased the efficiency of phosphorylation, which is the chemical reaction involving the addition of a phosphate group that is required for ATP synthesis.
• However, the horses that went through aerobic conditioning showed an improved efficiency of phosphorylation when under hyperthermic conditions.
• Similarly, acidosis, created by the addition of lactic acid, slightly hindered ATP synthesis in unconditioned horses
• Interestingly, the aerobic conditioning made the mitochondria more vulnerable to the harmful effects of acidosis.

Conclusion

• The research concluded that hyperthermia plays a major role in muscular fatigue during exercise, especially in less fit subjects as it notably impacts ATP synthesis and phosphorylation efficiency.
• Conversely, in fitter subjects who have undergone athletic conditioning, acidosis appears to be a more dominant factor causing failure of ATP synthesis.