Intracellular manganese ions provide strong T1 relaxation in rat myocardium.
The efficacy of manganese ions (Mn2+) as intracellular (ic) contrast agents was assessed in rat myocardium. T1 and T2 and Mn content were measured in ventricular tissue excised from isolated perfused hearts in which a 5-min wash-in with 0, 30, 100, 300, or 1000 microM of Mn dipyridoxyl diphosphate (MnDPDP) was followed by a 15-min wash-out to remove extracellular (ec) Mn2+. An inversion recovery (IR) analysis at 20 MHz revealed two T1 components: an ic and short T1-1 (650-251 ms), and an ec and longer T1-2 (2712-1042 ms). Intensities were about 68% and 32%, respectively. Tissue Mn content correlated particularly well with ic R1-1. A two-site water-exchange analysis of T1 data documented slow water exchange with ic and ec lifetimes of 11.3 s and 7.5 s, respectively, and no differences between apparent and intrinsic relaxation parameters. Ic relaxivity induced by Mn2+ ions in ic water was as high as 56 (s mM)(-1), about 8 times and 36 times higher than with Mn2+ aqua ions and MnDPDP, respectively, in vitro. This value is as high as any reported to date for any synthetic protein-bound metal chelate. The increased rotational correlation time (tauR) between proton and electron (Mn2+) spins, and maintained inner-sphere water access, might make ic Mn2+ ions and Mn2+ -ion-releasing contrast media surprisingly effective for T1-weighted imaging.
Nordhøy
Wibeke
W
Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim.
Anthonsen
Henrik W
HW
Bruvold
Morten
M
Brurok
Heidi
H
Skarra
Sissel
S
Krane
Jostein
J
Jynge
Per
P
D000704:Analysis of Variance; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage / Q000493:pharmacokinetics*; D005612:Freeze Drying; D006321:Heart / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D016018:Least-Squares Analysis; D008297:Male; D008345:Manganese / Q000008:administration & dosage / Q000493:pharmacokinetics*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D003287:Contrast Media; D008345:Manganese