title: Defective membrane systems in dystrophic skeletal muscle of the UM-X7.1 strain of genetically myopathic hamster.
abstract: 1. The function of mitochondria, sarcotubular membranes (heavy microsomes), sarcolemma and myofibrils from the hind-leg skeletal muscle of about 60- and 150-day-old normal and myopathic (UM-X7.1) hamsters was examined. 2. The mitochondrial calcium uptake as well as mitochondrial phosphorylation and respiratory rates were lower in 60-day-old myopathic skeletal muscle, unlike 150-day-old myopathic animals, when pyruvate-malate and glutamate-malate were used as substrates. However, mitochondria from 150-day-old myopathic animals showed depressed glutamate-dependent respiratory and phosphorylation rates and succinate-supported initial rate of calcium uptake. 3. The microsomal calcium-uptake, but not calcium-binding, and Ca2+-stimulated adenosine triphosphatase (ATPase) activity of the 150-day-old myopathic skeletal muscle were lower than the control values. Although microsomal calcium-binding, calcium-uptake and ATPase activities of the 60-day-old myopathic muscle were not depressed significantly, the initial rate of calcium uptake was less than the control. 4. The sarcolemmal Ca2+-ATPase, but not Mg2+-ATPase or Na+ +K+-ATPase, activity was higher in 60-day-old myopathic muscle whereas the activities of all these enzymes from 150-day-old myopathic animals were higher than the control. On the other hand, the Na+ +K+-ATPase activities from 60- and 150-day-old myopathic animals were inhibited by ouabain to a lesser extent in comparison with the respective control values. 5. The myofibrillar Ca2+-ATPase and Mg2+-ATPase activities as well as inhibition of Mg2+-ATPase due to Na+ and K+ in myopathic muscle were no different from the control values. 6. The results reported here give further support to the view that different membrane systems of the dystrophic muscle are defective.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000201:enzymology / Q000378:metabolism*; D009132:Muscles / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure*; D009137:Muscular Dystrophy, Animal / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D009210:Myofibrils / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption; D012508:Sarcolemma / Q000201:enzymology*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D010042:Ouabain; D000251:Adenosine Triphosphatases; D002118:Calcium