The bone-seeking agent99mTc-labeled 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) unexpectedly binds to particles of human articular cartilage as well as cortical bone in vitro. Collagen also sequesters this compound, suggesting that collagen contributes to the uptake of99mTc-HEDP by cartilage and bone. Particles of the bone mineral calcium hydroxyapatite also bind99mTc-HEDP in vitro. Pretreatment of particles with Er3+ stimulates binding in each case. Lowering the pH of incubation to pH 2 has this effect for bone, cartilage, and collagen, but not for calcium hydroxyapatite. Mechanisms additional to the simple ionic attraction between the phosphonate groups of HEDP and metal cations such as Ca2+ are responsible for the uptake of99mTc-HEDP by body tissues.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Orthopedics and Sports Medicine