Protracted Treatment of C57B1 Mice with Zn-DTPA after ²⁴¹Am Injection Reduces the Long-term Radiation Effects

Summary

Repeated intraperitoneal injections of ZnNa₃-diethylenetriaminepenta-acetate (ZnDTPA), once a week, during 8 successive weeks, and starting 4 days after injection of 58 and 373 kBq ²⁴¹Am/kg to C57B1 mice, were an effective protection against long-term radiation damage. At both dose levels of ²⁴¹Am, Zn-DTPA reduced the ²⁴¹Am concentration in bones by between 33% and 45%, and in the liver by 97%. Mean survival with ²⁴¹Am was shortened in Zn-DTPA-treated mice, by 17% at the lower dose level and by 70% at the higher dose level. After treatment with DTPA at the lower ²⁴¹Am level, survival became equal to that of control mice without ²⁴¹Am, while at the higher level life span was still shortened. After the lower ²⁴¹Am dose the incidence of bone tumours, liver carcinomas and the total number of all malignant tumours were significantly reduced by chelation therapy. The decrease in bone tumour incidence was proportional to the decrease in ²⁴¹Am concentration and reduction in cumulative radiation dose in bone after chelation therapy. The incidence of liver carcinomas was reduced to that in non-²⁴¹Am-injected mice and the reduction was thus proportional to the 97% reduction in ²⁴¹Am concentration of the liver at the end of chelation therapy. After the higher ²⁴¹Am dose no tumours showed up in sham-treated mice, probably due to the overkill effect on the cells at risk. In the corresponding Zn-DTPA-treated mice, bone tumours and a few other malignant tumours were observed.