Fractionated exposure of high energy iron ions has a sparing effect in vivo

We noted significantly lower levels of micronucleated reticulocytes in peripheral blood at 48 h after fractionated doses of iron ions when compared to the same total dose delivered in a single exposure demonstrating that protracted exposures of particle radiation resulted in an overall sparing effect in cytogenetic toxicity in the hematopoietic system in animals. Transgene mutation analysis revealed that fractionated delivery of iron doses was also effective in lowering the mutation yield in both brain and spleen tissues. However, this response is dose dependent. We conclude from these studies that fractioned doses of iron ions are effective in reducing the biological effectiveness in the end points used in these studies and that tissue physiology may play a role in defining the biological consequences after particle radiation exposure.