Dimensions of calcium release domains in frog skeletal muscle fibers

Julio L. Vergara; Marino DiFranco; David Novo

doi:10.1117/12.432488

2 July 2001 Dimensions of calcium release domains in frog skeletal muscle fibers

Julio L. Vergara, Marino DiFranco, David Novo

Proceedings Volume 4259, Biomarkers and Biological Spectral Imaging; (2001) https://doi.org/10.1117/12.432488
Event: BiOS 2001 The International Symposium on Biomedical Optics, 2001, San Jose, CA, United States

Abstract

The spatiotemporal properties of the Ca²⁺ release process in skeletal muscle fibers were determined using an improved confocal spot detection system. Muscle fibers were loaded with the low affinity fluorescent Ca²⁺ indicator OGB-5N and localized action potential-induced fluorescence signals were recorded from consecutive locations separated by 200 nm within a single sarcomere. Three-dimensional reconstructions on the Ca²⁺ transients illustrate the existence of domains of increased fluorescence around Ca²⁺ release sites in the neighborhood of the T-tubules. We estimated the dimensions of these domains by drawing isochronal curves ((delta) F/F vs. spot position) and fitting Gaussian profiles to them. It was found that the earliest detectable full-width-at-half- maximum of these profiles was 0.77 +/- 0.25 micrometers and increased rapidly with time to 1.4 +/- 0.2 micrometers at their peak (18 degree(s)C). A brief, but statistically significant delay of 0.8 +/- 0.42ms was observed between the onset of the fluorescent transients at the Z- and M-lines. Our results are compatible with the possibility that, in response to AP stimulation, Ca²⁺ is not released exclusively from the junctional region of the sarcoplasmic reticulum, but from a broader expanse of the triadic region.

Citation Download Citation

Julio L. Vergara, Marino DiFranco, and David Novo "Dimensions of calcium release domains in frog skeletal muscle fibers", Proc. SPIE 4259, Biomarkers and Biological Spectral Imaging, (2 July 2001); https://doi.org/10.1117/12.432488

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