ABSTRACT
The concentration dependence of the fluoride ion spin-lattice relaxation rate has been observed by nuclear magnetic resonance experiments on samples of defatted and dried bone. The 19F spin-lattice relaxation rates increased linearly with the bone fluoride concentration. Different results were obtained from trabecular than from cortical bone. For the same macroscopic fluoride content per gram of bone calcium, the relaxation rate is significantly faster in cortical bone. Relaxation rates in cortical bone samples prepared from both rats and dogs were apparently controlled by the same species-independent processes. For samples from beagle dogs, the bulk fluoride concentrations measured by neutron activation analysis were 3.1 +/- 0.3 times greater in trabecular bone than in the corresponding cortical bone. The beagle spin-lattice relaxation data suggest that the microscopic fluoride concentrations in bone mineral were 1.8 +/- 0.4 times greater in trabecular bone than in cortical bone. It is concluded that the accumulation of fluoride impurities in bone mineral is non-uniform.
Subject(s)
Bone Density , Bone and Bones/metabolism , Fluorides/metabolism , Animals , Dogs , Female , In Vitro Techniques , Magnetic Resonance Spectroscopy , Neutron Activation Analysis , Rats , Rats, Inbred StrainsABSTRACT
The 19F NMR properties of fluoridated rat bone powder samples have been studied in several external magnetic fields. The results show a characteristic field dependence, related to the strength of chemical shift interactions compared to dipole-dipole interactions. While the free induction decay shape is relatively insensitive to the 19F bone mineral concentration, the spin-lattice relaxation time decreases with increasing 19F concentration. Multi-exponential spin-lattice relaxation processes indicate that there are at least two chemically inequivalent incorporation sites for fluorine in bone mineral. Evidence for clustering of 19F fluoride impurities in bone mineral is seen in Hahn echo experiments. Sample preparation and handling methods are shown to affect the values of some of the observed NMR parameters.
