Biophys J, June 2001, p. 2658-2666, Vol. 80, No. 6

Calcium Waves in Agarose Gel with Cell Organelles: Implications of the Velocity Curvature Relationship

Manfred H. P. Wussling,^* Kirsten Krannich,^* Volker Drygalla, and Helmut Podhaisky

 ^*Julius Bernstein Institute of Physiology and  Institute of Numerical Mathematics, Martin Luther University Halle-Wittenberg, D-06097 Halle, Germany

Calcium oscillations and waves have been observed not only in several types of living cells but also in less complex systems of isolated cell organelles. Here we report the determination of apparent Ca²⁺ diffusion coefficients in a novel excitable medium of agarose gel with homogeneously distributed vesicles of skeletal sarcoplasmic reticulum. Spatiotemporal calcium patterns were visualized by confocal laser scanning fluorescence microscopy. To obtain characteristic parameters of the velocity curvature relationship, namely, apparent diffusion coefficient, velocity of plane calcium waves, and critical radius, positively and negatively curved wave fronts were analyzed. It is demonstrated that gel-immobilized cell organelles reveal features of an excitable medium. Apparent Ca²⁺ diffusion coefficients of the in vitro system, both in the absence or in the presence of mitochondria, were found to be higher than in cardiac myocytes and lower than in unbuffered agarose gel. Plane calcium waves propagated markedly slower in the in vitro system than in rat cardiac myocytes. Whereas mitochondria significantly reduced the apparent Ca²⁺ diffusion coefficient of the in vitro system, propagation velocity and critical size of calcium waves were found to be nearly unchanged. These results suggest that calcium wave propagation depends on the kinetics of calcium release rather than on diffusion.

Biophys J, June 2001, p. 2658-2666, Vol. 80, No. 6
© 2001 by the Biophysical Society   0006-3495/01/06/2658/09  $2.00

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