BIOLOGICAL EFFECTS OF (CSCL)-CS-137 INJECTED IN BEAGLE DOGS

The toxicity of intravenously administered (CsCl)-Cs-137 in the beagle dog was investigated as part of a program to evaluate the biological effects of internally deposited fission-product radionuclides. The int ravenous route of exposure was chosen for simplicity and accuracy beca use it was known that after intravenous injection, inhalation or inges tion, internally deposited (CsCl)-Cs-137 is rapidly absorbed and distr ibuted throughout the body, exposing the whole body to beta-particle a nd gamma radiations. Fifty-four dogs were injected intravenously with Cs-137 to provide one group of six dogs with mean initial body burdens of 141 MBq Cs-137/kg body mass and four groups of 12 dogs each with m ean initial body burdens of 104, 72, 52 and 36 MBq Cs-137/kg. Twelve d ogs were injected with isotonic saline as study controls. Because the number of study control dogs was small, data from an additional 49 con trol dogs from other studies at the Inhalation Toxicology Research Ins titute that were performed over a similar span of years were also used . There was a significant, dose-dependent decrease in survival of the Cs-137-injected dogs. Eleven Cs-137-injected dogs, including all six i n the highest initial body burden group, died within 81 days after inj ection, primarily due to hematopoietic cell damage resulting in severe pancytopenia. An additional 25 dogs had transient hematological dyscr asia but survived for long times. All Cs-137-injected male dogs had ma rked damage to the germinal epithelium of the testicular seminiferous tubules with azoospermia in the long-term survivors. Benign and malign ant neoplasms occurred in a variety of organs in Cs-137-injected dogs, rather than in a single target organ. When individual organs were con sidered, the incidence of malignant neoplasms was increased in the liv er and in the nasal cavity and paranasal sinuses of the Cs-137-injecte d dogs. There was a Cs-137 treatment effect in the incidence of malign ant neoplasms (P < 0.001) in male dogs but no Cs-137-related treatment effect in female dogs. However, when malignant mammary neoplasms were excluded from the analysis, there was no gender difference, and there was a dose-related response (P < 0.001) in both males and females for the incidence of malignant neoplasms. (C) 1995 by Radiation Research Society