Observations on the mechanism of 99mTc-labeled phosphate complex uptake in metabolic bone disease.

This communication describes a series of clinical and animal in vivo and in vitro investigations designed to elucidate the mechanism of 99mTc-Sn-phosphate complex concentration in metabolic bone disease. Rachitic and lathyritic animals were used as experimental models. Based on these studies it is concluded that 99mTc alters the pharmacology of the phosphate complexes, in particular pyrophosphate, which was the test agent most extensively employed, so that the usual affinity for mineral is for the greater part replaced by organic matrix binding. There is also evidence to suggest the immature collagen moiety of the organic matrix is the prime target of 99mTc-Sn-phosphate complex binding. Specifically, the aldehyde groups of the collagen molecule are suspected as being the major site of interaction.