title: Cable parameters, sodium, potassium, chloride, and water content, and potassium efflux in isolated external intercostal muscle of normal volunteers and patients with myotonia congenita.
abstract: In isolated fiber bundles of external intercostal muscle from each of 13 normal volunteers and each of 6 patients with myotonia congenita, some or all of the following were measured: concentrations of Na(+), K(+), and Cl(-), extracellular volume, water content, K(+) efflux, fiber size, fiber cable parameters, and fiber resting potentials. Muscle from patients with myotonia congenita differed significantly (0.001 <P< 0.025) with respect to the following mean values (myotonia congenita vs. normal): the membrane resistance was greater (5729 vs. 2619 omega.cm(2)), the internal resistivity was less (75.0 vs. 123.2 omega.cm), the water content was less (788.2 vs. 808.2 ml/kg wet weight), and the mean resting potential was greater (68 vs. 61 mv).NO SIGNIFICANT DIFFERENCES WERE FOUND WITH RESPECT TO THE FOLLOWING VARIABLES: K(+) content (73.5 vs. 66.7 mEq/kg wet weight) and the calculated intracellular K(+) concentration (215 vs. 191 mEq/liter fiber water), fiber capacitance (5.90 vs. 5.15 muf/cm(2)), Na(+) content (97.7 vs. 94.1 mEq/kg wet weight), Cl(-) content (79.0 vs. 74.7 mEq/kg wet weight), mannitol extracellular volume (45.1 vs. 46.6 cc/100 g wet weight), and K(+) efflux (23.2 vs. 21.5 moles x 10(-12) cm(-2).sec(-1)). These abnormalities of skeletal muscle in human myotonia congenita are like those of skeletal muscle in goats with hereditary myotonia. We tentatively conclude that a decreased Cl(-) permeability accounts for some of the abnormal electrical properties of skeletal muscle in myotonia congenita.
mesh_terms: D000200:Action Potentials; D000328:Adult; D001692:Biological Transport; D001706:Biopsy; D002712:Chlorides / Q000032:analysis; D005110:Extracellular Space / Q000032:analysis; D005260:Female; D006801:Humans; D007366:Intercostal Muscles / Q000032:analysis / Q000473:pathology / Q000503:physiopathology; D007477:Ions; D008055:Lipids / Q000032:analysis; D008297:Male; D009210:Myofibrils; D009224:Myotonia Congenita / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D011188:Potassium / Q000032:analysis; D011194:Potassium Isotopes; D011865:Radioisotope Dilution Technique; D012964:Sodium / Q000032:analysis; D014867:Water / Q000032:analysis
chemical_list: D002712:Chlorides; D007477:Ions; D008055:Lipids; D011194:Potassium Isotopes; D014867:Water; D012964:Sodium; D011188:Potassium