Divergent Modification of Low-Dose ^sup 56^Fe-Particle and Proton Radiation on Skeletal Muscle

It is unknown whether loss of skeletal muscle mass and function experienced by astronauts during space flight could be augmented by ionizing radiation. In this paper, adult mice were irradiated whole-body with either a single dose of 15 cGy of 1 GeV/n 56Fe-particle or with a 90 cGy proton of 1 GeV/n proton particles. Both ionizing radiation types caused alterations in the skeletal muscle cytoplasmic Ca^sup 2+^ ([Ca2+]i) homeostasis. ^sup 56^Fe-particle irradiation also caused a reduction of depolarizationevoked Ca2+ release from the sarcoplasmic reticulum. Protein analysis revealed significant increase in the phosphorylation of Akt, Erk1/2 and rpS6k on day 7 in ^sup 56^Fe-particle irradiated skeletal muscle, but not proton or unirradiated skeletal muscle, suggesting activation of pro-survival signaling. Findings suggest that a single low-dose ^sup 56^Fe-particle or proton exposure is sufficient to affect Ca^sup 2+^ homeostasis in skeletal muscle.