Toxicity of Radioiodine and Radiophosphorus in Rats in Doses Comparable To Those Used Clinically. ∗

Summary and Conclusions

1. Radioactive phosphorus (P³²) was administered by intubation to young male rats in doses equivalent to 4.6 mc. 7.0 mc and 11.6 mc for a 70 kg man. Similar radioiodine doses of I¹³¹ equivalent to 14.0 mc, 42, and 420 mc were given. All animals were sacrificed 6 weeks after dosing. 2. Except for a significant decrease in the testes body weight ratio and a moderate lymphopenia at the time of autopsy no growth curve, organ weight or histologic evidence of damage was discerned in the animals receiving P³². 3. Although no changes in weight gain or histologic evidence of organ damage was observed following the administration of I¹³¹, some variations in organ weight/body weight ratio were recorded. 4. In the doses here employed, which were comparable to those used clinically, no evidence of serious radiation damage was recorded.