Microdistribution of 239Pu in the rat skeleton. Part I. Dose dependency.

Sixty-day-old male and female rats were injected intravenously with one of three doses of monomeric 239Pu (1.11, 11.1 and 111 kBq kg-1 body weight) and were killed 1, 7, 14 or 32 days after injection. The macroscopic distribution in the skeleton as well as the microscopic distribution in the distal femur and the lumbar vertebra were studied. In general, no significant differences between the two sexes and the normalized three dose levels were found. The concentrations and dose-rates in hard tissue, marrow and near bone surfaces were lowest in the femur diaphysis and highest in the distal femur metaphysis. In each bone region the dose-rate increased in the order marrow, hard tissue, periosteal and endosteal bone surfaces. The initial dose-rates on the endosteal bone surfaces ranged from 130 mGy d-1 (femur diaphysis) up to 300 mGy d-1 (distal femur metaphysis), corresponding to an average cumulative monthly dose of 2.2 Gy (femur diaphysis) and 7 Gy (distal femur metaphysis) normalized to an injected dose of 37 kBq kg-1 body weight. After the injection of 111 kBq kg-1 body weight radiation, induced morphological changes occur to the distal femur metaphysis 32 days after injection.