Heavy-ion radiation accounts for the major component of absorbed cosmic radiation and is thus regarded as a significant risk during long-term manned space missions. To evaluate the genetic damage induced by heavy particle radiation, gpt delta transgenic mice were exposed to carbon particle irradiation and the induced mutations were compared with those induced by reference radiations, i.e., X-rays and gamma-rays. In the transgenic mouse model, deletions and point mutations were individually identified as Spi(-) and gpt mutations, respectively. Two days after 10 Gy of whole-body irradiation, the mutant frequencies (MFs) of Spi(-) and gpt were determined. Carbon particle irradiation significantly increased Spi(-) MF in the liver, spleen, and kidney but not in the testis, suggesting an organ-specific induction of mutations by heavy-ion irradiation. In the liver, the potency of inducing Spi(-) mutation was highest for carbon particles (3.3-fold increase) followed by X-rays (2.1-fold increase) and gamma-rays (1.3-fold increase), while the potency of inducing gpt mutations was highest for gamma-rays (3.3-fold increase) followed by X-rays (2.1-fold increase) and carbon particles (1.6-fold increase). DNA sequence analysis revealed that carbon particles induced deletions that were mainly more than 1,000 base pairs in size, whereas gamma-rays induced deletions of less than 100 base pairs and base substitutions. X-rays induced various-sized deletions and base substitutions. These results suggest that heavy-ion beam irradiation is effective at inducing deletions via DNA double-strand breaks but less effective than X-ray and gamma-ray irradiation at producing oxidative DNA damage by free radicals.

This study was conducted to explore the relationship between physicochemical property and toxic effectiveness using rat red blood cells (RBCs). The toxic effectiveness of acid nonsteroidal anti-inflammatory drugs (NSAIDs) was systemically examined by the depletion of intracorpuscular adenosine triphosphate (ATP), glutathione (GSH), and hemoglobin (Hb) at various doses, increased every 5 fmol/RBC. When the RBCs were incubated with NSAIDs, the drugs attained maximum levels within RBC, and the levels were then reduced. The ATP depletion seemed to be observed on the excretion of the drugs prior to the depletions of GSH and Hb. The physicochemical properties of NSAIDs were obtained from QMPRPlus, SMILES code, and CS ChemRaw Ultra. Correlation between their physicochemical properties and their doses for the depletions of ATP, GSH and Hb was performed in comparison with those of the membrane bound enzyme (MBE) inhibiting- and methemoglobin (MHb)-generating drugs. The ATP depletion by NSAIDs was correlated with the GSH depletion and intracorpuscular levels of the drugs, but not with the Hb depletion. The GSH depletion was correlated with the Hb depletion and participated in the lipophilicity of the drugs.