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Use of phosphocreatine kinetics to determine the influence of creatine on muscle mitochondrial respiration: an in vivo ³¹P-MRS study of oral creatine ingestion

¹Neuromuscular Function Laboratory, Department of Occupational Therapy, Temple University, Philadelphia, Pennsylvania 19140; ²United States Army Research Institute of Environmental Medicine, Natick 01760; ³Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston 02115; and ⁴Boston University, Sargent College of Health and Rehabilitation Sciences, Boston, Massachusetts 02215

Submitted 23 September 2003 ; accepted in final form 3 February 2004

ABSTRACT

Recent human isolated muscle fiber studies suggest that phosphocreatine (PCr) and creatine (Cr) concentrations play a role in the regulation of mitochondrial respiration rate. To determine whether similar regulatory mechanisms are present in vivo, this study examined the relationship between skeletal muscle mitochondrial respiration rate and end-exercise PCr, Cr, PCr-to-Cr ratio (PCr/Cr), ADP, and pH by using ³¹P-magnetic resonance spectroscopy in 16 men and women (36.9 ± 4.6 yr). The initial PCr resynthesis rate and time constant (T_c) were used as indicators of mitochondrial respiration after brief (10–12 s) and exhaustive (1–4 min) dynamic knee extension exercise performed in placebo and creatine-supplemented conditions. The results show that the initial PCr resynthesis rate has a strong relationship with end-exercise PCr, Cr, and PCr/Cr (r > 0.80, P < 0.001), a moderate relationship with end-exercise ADP (r = 0.77, P < 0.001), and no relationship with end-exercise pH (r = -0.14, P = 0.34). The PCr T_c was not as strongly related to PCr, Cr, PCr/Cr, and ADP (r < 0.77, P < 0.001–0.18) and was significantly influenced by end-exercise pH (r = -0.43, P < 0.01). These findings suggest that end-exercise PCr and Cr should be taken into consideration when PCr recovery kinetics is used as an indicator of mitochondrial respiration and that the initial PCr resynthesis rate is a more reliable indicator of mitochondrial respiration compared with the PCr T_c.

skeletal muscle; creatine kinase; mitochondria; phosphocreatine; phosphorous-31 magnetic resonance spectroscopy

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				A. M. Jones, D. P. Wilkerson, and J. Fulford Influence of dietary creatine supplementation on muscle phosphocreatine kinetics during knee-extensor exercise in humans Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2009; 296(4): R1078 - R1087. [Abstract] [Full Text] [PDF]

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