Autoradiography of 90Sr in developing rats

The distribution patterns of 90Sr in five littermate, 8-day-old Wistar rats were studied by whole body autoradiography. Rats were killed 15 min, 1, 4, 24, and 72 h after a single intraperitoneal injection of the isotope. Immediately after administration, 90Sr was distributed throughout most of the soft tissues of the body. The soft tissue deposits had practically disappeared after 4 h. In the hard tissues of the body 90Sr accumulated up to 24-72 h. Fifteen minutes after injection the uptake of 90Sr in the enamel of the teeth was highest in the occlusal and incisal regions. 90Sr gradually accumulated throughout the enamel and after 72 h its distribution in this layer was fairly uniform. Immediately after injection a narrow zone of radioactivity appeared in the dentin near the pulp. This zone broadened with time towards the dentinoenamel junction and included the entire dentin layer 72 h after injection. Initially, the uptake of 90Sr was higher in the dentin thatn in the enamel, particularly in the cervical areas of the crown. This difference became less apparent with time. There was good correlation between the uptake in teeth and bones, supporting the use of teeth as indicators of the 90Sr body burden.