title: Comparison of ionic and non-ionic nitroxide spin labels for urographic enhancement in magnetic resonance imaging.
abstract: Two nitroxide spin labels (NSL) were compared for in vitro relaxivity and in normal rats for efficiency of urographic enhancement. One of the NSL, PCA, a pyrrolidinyl agent, was ionic and one, NAT, was a non-ionic pyrrolidinyl NSL with multiple hydroxyl substituents for water solubility. Using both NSLs the renal medulla and papilla were noted to show greater contrast enhancement than the cortex, with a maximum enhancing effect between 5 and 15 minutes. Using doses of 1.0 and 2.5 mmol/kg, more than 100 per cent increases in spin echo intensities above the baseline were observed. The lowest tested dose of 0.1 mmol/kg showed an easily detectable enhancing effect for NAT. The good contrast enhancing properties of NAT, considered together with its better acute tolerance, justifies further investigation of this non-ionic compound.
mesh_terms: D000818:Animals; D003497:Cyclic N-Oxides; D007668:Kidney / Q000033:anatomy & histology*; D007672:Kidney Cortex / Q000032:analysis; D007679:Kidney Medulla / Q000032:analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051381:Rats; D011919:Rats, Inbred Strains; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D013113:Spin Labels; C032289:2,2,5,5-tetramethyl-1-pyrrolidinyloxy-3-carboxylic acid; C050028:N-1-hydroxymethyl-2,3-dihydroxypropyl-2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-carboxamide