Skeletal muscle mitochondrial myopathy as a cause of exercise intolerance in a horse

S. J. Valberg, G. P. Carlson, G. H. Cardinet, E. K. Birks, J. H. Jones, A. Chomyn, S. Dimauro

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)305-312
Number of pages8
JournalMuscle and Nerve
Issue number3
StatePublished - 1994


  • Complex I
  • horse
  • mitochondria
  • muscle
  • myopathy

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)


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