Intracellular Mg2+ diffusion within isolated rat skeletal muscle fibers
2001
Claude Bernengo, Jean | COLLET, Claude | Jacquemond, Vincent
Intracellular free magnesium concentration Mg was measured in enzymatically isolated rat skeletal muscle fibers using the fluorescent dye mag-indo-1. The change in Mg produced by a local intracellular microinjection of magnesium pidolate magnesium pyrrolidone carboxylate was measured at a given distance from the injection site. In one series of experiments this protocol was tested on isolated fibers that were completely embedded into silicone grease: under these conditions, the injection produced an increase in Mg that reached a steady level some time following the injection. The time-course of the Mg change could be well accounted for by a model of longitudinal diffusion. The mean apparent Mg diffusion coefficient. Dapp was 188 + 9 µm2 s-1 (n=16), approximately four times lower than the value measured in vitro. This reduction likely results from the effects of cytoplasmic viscosity and of Mg2q binding to low affinity static sites. Another series of measurements was performed on fibers that were either partially or completely free of silicone: under these conditions, the time course of the change in Mg was in many cases more complex than predicted by simple diffusion.
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