Further impairment of muscle phosphate kinetics by lengthening exercise in DMD/BMD carriers. An in vivo 31P-NMR spectroscopy study.
We used phosphorus magnetic resonance spectroscopy (31P-MRS) to study the effect of exercise-induced muscle injury in the calf muscle of 7 DMD/BMD carriers and 6 non-carrier females. All subjects performed 50-80 lengthening contractions with the right calf muscles. 48 h after lengthening exercise non-carriers showed increased sensitivity to pressure in their gastrocnemius accompanied by increased T2 relaxation times and by elevated Pi/PCr ratios at rest. DMD/BMD carriers did not show any effect of lengthening exercise on these measurements. In-magnet exercise revealed in all carriers a reduced initial rate of Pi recovery and an increased time to fully recovery the resting value of intracellular pH. Lengthening exercise further decreased the initial rate of Pi recovery. Non-carriers did not show any variation attributable to lengthening exercise either during in-magnet work or during recovery from exercise. We found that lengthening exercise contractions causes: (1) less muscle injury in carriers compared to non-carriers, (2) even slower rate of Pi recovery, but (3) no effect on Pi recovery in non-carriers. The use of lengthening exercise and measurements of Pi recovery may be a useful method to evaluate the disease process in DMD/BMD.
Barbiroli
B
B
Cattedra di Biochimica Clinica, Università di Bologna, Italy.
McCully
K K
KK
Iotti
S
S
Lodi
R
R
Zaniol
P
P
Chance
B
B
D000293:Adolescent; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006579:Heterozygote; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009132:Muscles / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D009136:Muscular Dystrophies / Q000378:metabolism* / Q000473:pathology; D010710:Phosphates / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D010759:Phosphorus Isotopes
D010710:Phosphates; D010759:Phosphorus Isotopes; D010725:Phosphocreatine