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Longitudinal proton relaxation rates in rabbit tissues after intravenous injection of free and chelated Mn 2+
Author(s) -
Spiller Marga,
Brown Rodney D.,
Koenig Seymour H.,
Wolf Gerald L.
Publication year - 1988
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910080307
Subject(s) - chemistry , chelation , relaxation (psychology) , proton , paramagnetism , nuclear magnetic resonance , ion , mri contrast agent , compartmentalization (fire protection) , kidney , gadolinium , inorganic chemistry , biochemistry , endocrinology , medicine , physics , organic chemistry , quantum mechanics , enzyme
The factors that determine the field‐dependent increase in 1/ T 1 of tissue water protons were investigated for MnCl 2 , and Mn 2+ (PDTA) (1, 3‐propylenediamine‐ N , N ′, N ″, N ‴‐tet‐ raacetic acid) introduced intravenously into rabbits. Mn 2+ was used in preference to other paramagnetic ions in part because of the distinct NMRD profiles (magnetic field dependence of 1/ T 1 ) of free Mn 2+ ions, their small chelate complexes, and their macromolecular conjugates, and in part because the relatively low toxicity of Mn 2+ is favorable for animal studies. Tissue content of Mn 2+ was determined in all samples by inductively coupled plasma analyses; the state of Mn 2+ in excised tissues was determined from the form of the 1/ T 1 NMRD profile of water protons; and distribution of contrast agent within tissue and access of water on a T 1 time scale were determined by double‐exponential analyses of proton relaxation behavior in intact doped tissue, as well as by the change of single‐exponential relaxation rates and proton signal intensity upon gentle disruption ofthe tissue. MnCl 2 is found in all tissues, except fat and skeletal muscle, but liver is most avid at low dose, and Mn 2+ accumulates in spleen after high doses. Chelation targets Mn 2+ to liver and kidney, saturating the liver chemically at relatively low dose. We suggest that pronounced increase in tissue relaxivity results from irrotationally bound Mn 2+ , ostensibly associated with the polar head groups of cell membranes. Compartmentalization of contrast agent and restricted diffusion of tissue water influences the maximum relaxation rates attainable, so that there is an optimal dose of these contrast agents which is rather low. © 1988 Academic Press, Inc.