Uptake and Retention of Strontium 90 in Mouse Tissues Studied by Whole Animal Autoradiography and Impulse Counting. I

Abstract

Autoradiograms were made from sagittal sections through whole frozen animals and from methylacrylate-embedded femurs; the intervals between injection of Sr90 and examination of the 36 mice ranged from 5 minutes to 10 months and a Sr90 staircase was used to facilitate quantitative evaluation of the auto-radiograms. In whole-body autoradiograms made shortly after injection, activity was seen in all tissues but gradually accumulated in the hard tissues and simultaneously declined in the soft tissues. By about 4 hours after injection all activity was limited to the hard tissues of the body and a redistribution within the hard tissues could be observed. By 5 minutes after injection Sr90 activity was greatest in bone accumulating specifically in growth zones. Fine subperiosteal and subendosteal lines were also discerned. Some of the soft tissue had a greater activity than the blood, E.G., the blood vessels, the cornea and sclera of the eye and the hair follicles. Excretion via the kidneys, the intestinal wall and the biliary tract were observed. Membranous bones of the skull showed double contours resulting from endosteal and periosteal uptake. Among the hard tissues of the head, the greatest Sr90 activity was noted in the teeth, particularly in the dentine adjacent to the pulp and in the occipital bone and the base of the skull. Certain bones such as the turbinate bones showed comparatively high uptake followed by a rapid decline, while other bones, e.g., the nasal bone had a lower initial uptake and slower rate of decline. Redistribution of Sr90 activity in the vertebral bodies was fundamentally similar to that in the bones of the extremities. The high uptake in the meta-physeal region almost totally disappeared after one month, and subsequently the activity in the diaphysis dominated the autoradiographic picture.