High-energy phosphate transfer in human muscle: the diffusion of phosphocreatine.

[Mike Bikov]

Am J Physiol Cell Physiol. 2011 Mar 2. [Epub ahead of print]
High-energy phosphate transfer in human muscle: the diffusion of phosphocreatine.

Gabr RE, El-Sharkawy AM, Schär M, Weiss RG, Bottomley PA.

Johns Hopkins University.
Abstract

The creatine kinase (CK) reaction is central to muscle energetics, buffering ATP levels during periods of intense activity via the consumption of phosphocreatine (PCr). PCr is believed to serve as a spatial shuttle of high-energy phosphate between sites of energy production in the mitochondria, and sites of utilization in the myofibrils, via diffusion. Knowledge of the diffusion coefficient of PCr, D(PCr), is thus critical for modeling and understanding energy transport in the myocyte, but has not been measured in humans. We measured D(PCr) in the calf muscle of eleven adults using localized phosphorus magnetic resonance spectroscopy as a function of direction and diffusion time. The results show that the diffusion of PCr is anisotropic with significantly higher diffusion along the muscle fibers, and that the diffusion of PCr is restricted to a path length of ~28μm assuming a cylindrical model, with an unbounded diffusion coefficient of ~0.69x10(-3) mm(2)/s. This distance is comparable in size to myofiber radius. Based on prior measures of CK reaction kinetics in human muscle, the expected diffusion distance of PCr during its half-life in the CK reaction is ~66 μm. This distance is much larger than the average distances between mitochondria and myofibrils. Thus, these first measurements of PCr diffusion in human muscle in vivo support the view that PCr diffusion is not a factor limiting high-energy phosphate transport between the mitochondria and the myofibrils in healthy resting myocytes.

PMID: 21368292 [PubMed - as supplied by publisher]​

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