Dynamics of Calcium Fluxes in Nonexcitable Cells: Mathematical Modeling |
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Authors: | Alfonsas Juška |
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Institution: | (1) Vilniaus Gedimino technikos universitetas, Saulėtekio al. 11, 10223, Vilnius-40, Lithuania |
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Abstract: | Mathematical models simulating the dynamics of calcium redistribution (elicited by experimental interference with the pathways
of calcium fluxes) in cellular compartments have been developed, based on a minimal scheme of the pathways of calcium fluxes
in nonexcitable cells suspended in calcium-free medium. The models are consistent with available experimental data. All parameters
are quantitatively related to the intrinsic properties of calcium adenosine triphosphatases (ATPases) and cellular membranes;
there is no interdependence between the parameters. The models can be used as the basis for quantitative analysis and interpretation
of experimental data. The activities of plasma membrane and sarcoendoplasmic reticulum calcium ATPases (PMCA and SERCAs) are
governed by different mechanisms. PMCA is likely to undergo transitions from inactive to active to “dormant” (not identical
to the initial) and back to inactive states, the mean duration of the cycle lasting for minutes or longer. The sequence of
the transitions is initiated, presumably, by an increase in cytosolic calcium concentration. The transition of PMCA from inactive
to active (at least at low rates of increase in cytosolic calcium concentration) is likely to be slower than that from active
to dormant. SERCA, presumably, transits from inactive to active state in response to increases in calcium leakage from calcium
stores. Whereas PMCA extrudes excess calcium (a definite quantity of it) in a short pulse, SERCA retakes calcium back into
the stores permanently at a high rate. The models presented here may be the best means for the moment to quantitatively relate
the dynamics of calcium fluxes in nonexcitable cells with known or putative properties of the mechanisms underlying activation
of calcium ATPases. |
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Keywords: | Cytosolic free calcium Calcium stores Endomembrane permeability Calcium leakage Calcium extrusion Calcium reuptake Calcium ATPases Ionomycin |
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