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Diffusional anisotropy is induced by subcellular barriers in skeletal muscle
S T Kinsey1, B R Locke, B Penke
1University of North Carolina at Wilmington, Department of Biological Sciences, NC 28403-3297, USA.
NMR in Biomedicine
|April 9, 1999
Summary
Phosphocreatine diffusion in fish muscle reveals time-dependent barriers. Pulsed-field gradient NMR showed diffusion is anisotropic, with sarcoplasmic reticulum and mitochondria limiting movement.
Area of Science:
- Biophysics
- Cellular Physiology
- Biochemistry
Background:
- Skeletal muscle intracellular diffusion is complex.
- Understanding diffusion barriers is key to muscle function.
- Previous models did not fully explain diffusion anisotropy.
Purpose of the Study:
- To investigate the time- and orientational-dependence of phosphocreatine diffusion in skeletal muscle.
- To identify intracellular structures responsible for diffusion anisotropy.
- To non-invasively probe intracellular diffusive barriers using PFG-NMR.
Main Methods:
- Utilized pulsed-field gradient nuclear magnetic resonance (PFG-NMR).
- Measured apparent diffusion coefficients (D) axially and radially in fish skeletal muscle.
- Examined diffusion over a time course from 12 to 700 ms at 5°C.
Main Results:
- Radial diffusion was time-dependent, decreasing until ~100 ms.
- Diffusion was anisotropic, with axial diffusion higher than radial.
- Sarcoplasmic reticulum (SR) and mitochondria were identified as principal diffusion inhibitors.
Conclusions:
- Intracellular structures like SR and mitochondria cause orientation-dependent diffusion.
- This is the first study to demonstrate diffusional anisotropy induced by identifiable intracellular structures.
- PFG-NMR is effective for non-invasively characterizing muscle intracellular diffusion barriers.