Peer-reviewed veterinary case report
Skeletal muscle mitochondrial myopathy as a cause of exercise intolerance in a horse.
- Journal:
- Muscle & nerve
- Year:
- 1994
- Authors:
- Valberg, S J et al.
- Affiliation:
- Department of Anatomy · United States
- Species:
- horse
Plain-English summary
A 10-year-old Arabian mare was found to have a serious problem that made it hard for her to exercise. Despite thorough examinations and tests, including blood work and heart scans, everything seemed normal at first. However, when she was gradually exercised, she developed a significant buildup of lactic acid in her muscles, which is a sign that her body wasn't using energy properly during activity. Muscle samples showed unusual changes in the tiny energy-producing parts of her cells, indicating a deficiency in an important enzyme needed for energy production. This condition was causing her exercise intolerance and muscle stiffness, and it was linked to her body's inability to generate energy effectively during exercise.
Abstract
Although exertional myopathies are commonly recognized in horses, specific etiologies have not been identified. This is the first report in the horse of a deficiency of Complex I respiratory chain enzyme associated with profound exercise intolerance. Physical examination, routine blood tests, endoscopy, and ultrasonograms of the heart and iliac arteries were unremarkable. With slow, incremental exercise (speeds 1.5-7 m/s), the Arabian mare showed a marked lactic acidosis, increased mixed venous PVO2, and little change in oxygen consumption. Muscle biopsies contained large accumulations of mitochondria with bizarre cristae formations. Biochemical analyses revealed a very low activity of the first enzyme complex in the mitochondrial respiratory chain (NADH CoQ reductase). The exercise intolerance and muscle stiffness in this horse were attributed to a profound lactic acidosis resulting from impaired oxidative energy metabolism during exercise.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/8107707/