Local blood flow, 99mTc-MDP retention and 85Sr retention in femur and tibia of rats: local differentiation and inter-relations

Variations were studied in blood flow, retention of 99mTc-methylenediphosphonate (MDP) and 85SrCl2 in the femur and in the tibia of rats. The objective of the experiments was to assert local differences in the blood flow and similar patterns, if any, in the retention of both radionuclides in the long bones of the hind leg of the rat. The results showed a significant differentiation in the blood flow in both the femur and the tibia, with high levels in the growth-active parts and low levels in the diaphyses. The lowest levels were found in the distal terminal part of the tibia. A marked similarity was observed in the patterns of blood flow distribution and 99mTc-MDP retention, this both in quality and in quantity. The retention was found to be significantly higher in the growth-active parts, i.e., in the distal methaphysis of the femur and in the proximal metaphysis os the tibia, while several times lower values were found for the other parts of the bones. However, age dependence was observed in the distribution and some other factors may play a role. Thus, a quantitative relationship was excluded. The initial retention of 85Sr showed a similar pattern with high levels in the growth-active parts of the bones. However, the values quickly decreased with time, which may have been associated with the metabolism of minerals. In the other parts of the bones, the differences in 85Sr retention were insignificant. It is believed that local blood flow may affect the behavior of both osteotropic materials as a common regulating factor. (L.O.). 3 figs., 1 tab., 22 refs