title: An abnormal exercise test response revealing a respiratory chain complex III deficiency.
abstract: A 29-year-old man with a progressive exertional muscle intolerance since childhood was referred for incremental exercise test on a bicycle ergometer. The response pattern suggested a mitochondrial myopathy: that is, a greatly reduced maximum oxygen consumption with appropriate heart rate increase and an anaerobic threshold point reached early. The metabolic investigation in plasma revealed an abnormal oxidoreduction status (hyperlactataemia and high lactate/pyruvate ratio) at rest and after a carbohydrate rich meal. The histochemical examination of a muscle biopsy revealed red granular deposits under the sarcolemma for all type 1 fibers. Oxypolarographic and enzymological studies of the mitochondrial respiratory chain in both isolated mitochondria and muscle homogenate demonstrated a marked deficiency of ubiquinol cytochrome c reductase (complex III) activity.
authors.affiliation: Laboratoire de Biochimie Pédiatrique, Hôpital Debrousse, Lyon, France.
authors.forename: B
authors.initials: B
authors.lastname: Mousson
authors.forename: J M
authors.initials: JM
authors.lastname: Collombet
authors.forename: R
authors.initials: R
authors.lastname: Dumoulin
authors.forename: H
authors.initials: H
authors.lastname: Carrier
authors.forename: F
authors.initials: F
authors.lastname: Flocard
authors.forename: M
authors.initials: M
authors.lastname: Bouzidi
authors.forename: C
authors.initials: C
authors.lastname: Godinot
authors.forename: I
authors.initials: I
authors.lastname: Maire
authors.forename: M
authors.initials: M
authors.lastname: Mathieu
authors.forename: S
authors.initials: S
authors.lastname: Quard
mesh_terms: D000328:Adult; D004272:DNA, Mitochondrial; D014450:Electron Transport Complex III / Q000172:deficiency* / Q000378:metabolism; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D008297:Male; D017240:Mitochondrial Myopathies / Q000175:diagnosis / Q000201:enzymology / Q000503:physiopathology*; D009132:Muscles / Q000378:metabolism; D010101:Oxygen Consumption; D010949:Plasma / Q000378:metabolism; D012119:Respiration; D013385:Succinate Dehydrogenase / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D013385:Succinate Dehydrogenase; D014450:Electron Transport Complex III