Animal Studies of Residual Hematopoietic and Immune System Injury from Low Dose/Low Dose Rate Radiation and Heavy Metals

摘要

The interaction of low dose/low dose rate radiation with heavy metals (in this report cadmium and lead) is important for at least two reasons: 1) radiation workers and populations exposed to unusually high background levels of radiation (e.g. Chernobyl and the Techa river in Russia) receive this type of exposure rather than the much befter studied prompt high dose exposure, and 2) radiation accidents frequently involve the release of other contaminants as well. Even at low radiation doses and dose rates, the effects of simultaneous or near simultaneous exposure to cadmium or lead, which are marrow toxicants in their own right, are additive or synergistic to those of radiation. Although there is an adaptive response to low dose rate exposures, recovery of marrow precursor cells after a second exposure may be incomplete. Detection of damage repair changes after low dose exposures is difficult. The authors describe possible mechanisms for the observed delayed or incomplete recovery. They also address the complex pathogenic changes seen when heavy metals are introduced along with the radiation. The implications of their findings in rodent models for human populations are discussed, and the importance and proposed directions of farther work in this field described.