Model showing the Ca²⁺ fluxes in control and mdx fibers and the possible consequences of the changing of these fluxes on Ca²⁺ homeostasis in mdx fibers. Gray arrows correspond to Ca²⁺ fluxes. Partial filling with gray color of the SR compartment in mdx fibers indicates possible reduced SR Ca²⁺ content. Broken black arrows indicate that SR depletion and/or SR leak influence sarcolemmal Ca²⁺ influx and provoke in mdx fibers a higher sarcolemmal Ca²⁺ influx that contributes to higher cytosolic [Ca²⁺]. See text for details.