Abstract 14587: Different Sequence of Fractionated Proton and Single Low Dose Iron Radiation Induce Divergent Biological Responses in the Heart

Astronauts will be exposed to ionizing radiation (IR) composed of a spectrum of low-fluence protons (1H) and high charge and energy (HZE) nuclei iron (e.g., 56Fe). During GCR each cell in the body will be traversed by 1H every 3-4 days and HZE nuclei every few months. The effects of sequential/fractionated low doses of 1H or HZE on cardiovascular system are unknown. Male C57BL/6NT mice of 8-9 month old were evaluated over 3 months: Group 1- control; Group 2 - 1H 17 cGy every 2 days/3 doses; Group 3 - 1H 17 cGy every 2 days/3 doses followed by a single dose of 56Fe 15 cGy 2 days after the last dose of 1H; Group 4 - a single dose of 56Fe 15 cGy/followed by fractionated 1H 17 cGy every 2 days/3 doses 2 days after a single 56Fe-IR; at 1 GeV energy for both ions. Cardiac function, cardiac fibrosis and cardiac remodeling were assessed by echocardiography, hemodynamic measurements, Hu0026E and Trichrome staining. In IR + Aging group, over 3 months, 1H+1H+1H-IR alone or 1H+1H+1H/56Fe-IR did not induce negative effect...