Oral Presentation 2014 International Biophysics Congress

Comparison of simulated calcium sparks and calcium sparks recorded in intact amphibian skeletal muscle (#45)

Janos Vincze 1 , Henrietta Cserné Szappanos 1 2 , Péter Szentesi 1 , Dóra Bodnár 1 , László Z. Szabó 3 , Martin F. Schneider 2 , László Csernoch 1
  1. University of Debrecen, Debrecen, Hungary
  2. University of Maryland, Baltimore, MD, USA
  3. Sapientia Hungarian University of Transylvania, Târgu Mureș, Romania

High-speed confocal microscopy has enabled the imaging of calcium sparks in muscle cells with a highly increased temporal resolution, including the recording of X-Y image series showing undistorted sparks.

Calcium sparks in intact amphibian skeletal muscle cells under control conditions, during subthreshold depolarization (-70 to -60 mV) and treatment with caffeine (1 mmol/l) were recorded in X-Y scan mode using a Zeiss LSM 5 LIVE high-speed confocal microscope. A wavelet transform-based automatic analysis algorithm developed by our group was used for image analysis. Images were generated using simulated sparks with different spatial distributions and spark parameters for comparison.

Under control conditions, spatial distribution of the few (frequency: 0.081±0.02 ms-1µm-2) calcium sparks was not homogeneous in the cell as sparks appeared in hot spots and closer to the Z-line (mode of distance: 0.2 µm). Their positions did not depend on that of each other, however, as the distribution of spark centre to spark centre distance did not differ significantly (p=0.33) from the linear relationship produced by independently located simulated sparks. Depolarization and caffeine treatment increased spark frequency (to 1.31±0.37 and 0.26±0.09 ms-1µm-2, respectively) by activating RyRs homogeneously across the whole cell. Sparks further away from the Z-line were elicited (mode of distance: 0.4 µm) and the distribution of the spark-to-spark distance became quadratic (p<0.0001 vs. linear) in both groups.

In conclusion, both depolarization and caffeine treatment have effects on the spatial distribution of calcium sparks which are beyond what is caused by the increase in the spark frequency. Simulation of skeletal muscle calcium sparks may lead to a better understanding of the underlying processes.