The effects of inhaled (PuO2)-Pu-238 deposited in the liver of dogs we
re studied in beagles exposed to initial lung depositions ranging from
5.7 to 2979.7 Bq/g lung. Approximately 20% of the initial lung deposi
tion was translocated to the liver by 1500 days after exposure. Life-s
pan observations revealed that the liver contained 40% of the final bo
dy burden of plutonium, second only to the skeleton. Elevated serum li
ver enzyme activities were observed in dogs with final liver depositio
ns of greater than or equal to 0.4 Bq/g, cumulative dose to the liver
of greater than or equal to 0.18 Gy and annual dose rate greater than
or equal to 0.02 Gy/year. Enzyme elevations were seen at one dose leve
l lower than that in which bone or lung tumors were observed. Linear r
egression analysis revealed strong to moderate correlation between cum
ulative dose and dose rate and time to observed increases in liver enz
yme activities. Liver tumors were late-occurring neoplasms observed at
lower exposure levels where life span was not shortened by lung and b
one tumors. (C) 1995 by Radiation Research Society