Influence of transition metal ions on NMR proton T1 relaxation times of serum, blood, and red cells

The spin-lattice relaxation rates (1/T1) of serum, whole blood, and red cel ls were measured vs several concentrations of transition metal ions. For co mparative purposes, the similar experiments were repeated in water. The rat es show a linear dependence on concentration of each ion for water, but nea rly a linear dependence for blood and its constituents. The influence of ea ch ion on 1/T1 in a sample was expressed by the slope (relaxivity) of the l east-squares fitting of 1/T1 vs ion concentration. The relaxivities of Mn(I I) in serum and of Fe(III) in serum and blood are greater than those in wat er, whereas the relaxivities of these ions in the other cases and of all th e other ions in call cases are smaller than those in water. However, the re laxivity data show that Cr(III) in serum and blood affects the 1/T1 rates. The ratio of relaxivity of each sample to that of water is known as proton relaxation enhancement (PRR) factor (epsilon). The epsilon factors for pres ent data suggest that the added ions are bound to proteins, and only Mn(II) in serum and Fe(III) in blood and serum are accessible to water.