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Diffusional anisotropy is induced by subcellular barriers in skeletal muscle
Author(s) -
Kinsey Stephen T.,
Locke Bruce R.,
Penke Brigita,
Moerland Timothy S.
Publication year - 1999
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/(sici)1099-1492(199902)12:1<1::aid-nbm539>3.0.co;2-v
Subject(s) - skeletal muscle , biophysics , chemistry , anisotropy , myosin , intracellular , nuclear magnetic resonance , diffusion , muscle relaxation , anatomy , biochemistry , biology , physics , optics , thermodynamics , endocrinology
The time‐ and orientational‐dependence of phosphocreatine (PCr) diffusion was measured using pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) as a means of non‐invasively probing the intracellular diffusive barriers of skeletal muscle. Red and white skeletal muscle from fish was used because fish muscle cells are very large, which facilitates the examination of diffusional barriers in the intracellular environment, and because they have regions of very homogeneous fiber type. Fish were cold‐acclimated (5°C) to amplify the contrast between red and white fibers. Apparent diffusion coefficients, D , were measured axially, D ∥ , and radially, D ⟂ , in small muscle strips over a time course ranging from 12 to 700 ms. Radial diffusion was strongly time dependent in both fiber types, and D ⟂ decreased with time until a steady‐state value was reached at a diffusion time ≊ 100 ms. Diffusion was also highly anisotropic, with D ∥ being higher than D ⟂ for all time points. The time scale over which changes in D ⟂ occurred indicated that the observed anisotropy was not a result of interactions with the thick and thin filament lattice of actin and myosin or restriction within the cylindrical sarcolemma, as has been previously suggested. Rather, the sarcoplasmic reticulum (SR) and mitochondria appear to be the principal intracellular structures that inhibit mobility in an orientation‐dependent manner. This work is the first example of diffusional anisotropy induced by readily identifiable intracellular structures. Copyright © 1999 John Wiley & Sons, Ltd.