Contribution of paramagnetic trace elements to the spin-lattice relaxation time in the liver

The relaxation times of water protons in rat liver tissue were measured with a NMR spectrometer at 20 MHz. The paramagnetic trace elements Cu, Fe, and Mn were determined by neutron activation analysis. No shortening of T1 could be observed when liver Cu or Fe concentration was increased in the microgram range. T1 was strongly correlated with the liver Mn concentration of untreated animals and animals whose liver Mn concentration was artificially increased or decreased by intravenous injection of manganous acetate or a metal chelating agent with high affinity for hepatobiliary excretion. Deviations from this Mn-T1 correlation were found in the initial phase of liver cirrhosis induced by thioacetamide (elongated T1, normal Mn concentration) and after stimulation of liver growth by phenobarbital (normal T1, decreased Mn concentration). An increased or decreased enhancement factor for Mn may have contributed to the observed deviations during phenobarbital and thioacetamide treatment.