The Retention, Distribution, Dose and Cytogenetic Effects of 241Am Citrate in the Chinese Hamster

Abstract

Chinese hamsters were injected intraperitoneally with 3.3 × 10−2 or 1 × 1O−3 μCi 241Am citrate/g body weight and sacrificed at 1, 2, 4, 8, 16, 32, 64, 225 and 360 days post-injection to determine the tissue distribution and to calculate the radiation dose to the liver and bone. After a rapid early clearance, the whole-body retention of the 241Am decreased with an effective half life of approximately 1000 days. The liver and skeleton contained 50 and 20%, respectively, of the initial body burden at 360 days post-injection. Other animals were injected with 1 × 10−1, 3 × 10−2, 1 × 10−2 and 5 × 10−3 μCi 241Am citrate/g body weight; their mean survival times were 36, 91, 138 and 342 days, respectively, with one control death occurring before 400 days. The most frequent pathological alterations noted were bone marrow hypoplasia and biliary and nodular hyperplasia in the liver. Additional hamsters were injected with graded levels of activity from 5 × 10−3 to 6 × 10−7 μCi 241Am citrate/g body weight. These animals were sacrificed at 6, 15, 42, 122 and 362 days post-injection to determine the frequency of metaphase chromosome aberrations in the liver following partial-hepatectomy to stimulate hepatic cell division and administration of colchicine to accumulate cells in metaphase. The frequency of aberrations/cell in the liver increased linearly with cumulative radiation dose with an aberration coefficient of 7.1 × 10−3 aberrations/cell/rad. There was no change in the effectiveness of the dose per rad for producing aberrations over a dose rate range of 0.05–10 rads/day. Americium-241 was about 20 times more efficient per rad than protracted 144Ce − 144Pr exposures in producing chromosome aberrations.