Hepatic effects of inhaled plutonium dioxide in beagles.

The effects of inhaled 238PuO2 deposited in the liver of dogs were studied in beagles exposed to initial lung depositions ranging from 5.7 to 2979.7 Bq/g lung. Approximately 20% of the initial lung deposition was translocated to the liver by 1500 days after exposure. Life-span observations revealed that the liver contained 40% of the final body burden of plutonium, second only to the skeleton. Elevated serum liver enzyme activities were observed in dogs with final liver depositions of > or = 0.4 Bq/g, cumulative dose to the liver of > or = 0.18 Gy and annual dose rate > or = 0.02 Gy/year. Enzyme elevations were seen at one dose level lower than that in which bone or lung tumors were observed. Linear regression analysis revealed strong to moderate correlation between cumulative dose and dose rate and time to observed increases in liver enzyme activities. Liver tumors were late-occurring neoplasms observed at lower exposure levels where life span was not shortened by lung and bone tumors.