title: Inhibition of the sodium-calcium exchanger via SEA0400 altered manganese-induced T1 changes in isolated perfused rat hearts.
abstract: Manganese (Mn(2+) )-enhanced MRI (MEMRI) provides the potential for the in vivo evaluation of calcium (Ca(2+) ) uptake in the heart. Recent studies have also suggested the role of the sodium-calcium (Na(+) -Ca(2+) ) exchanger (NCX) in Mn(2+) retention, which may have an impact on MEMRI signals. In this study, we investigated whether MEMRI with fast T(1) mapping allowed the sensitive detection of changes in NCX activity. We quantified the dynamics of the Mn(2+) -induced T(1) changes in isolated perfused rat hearts in response to SEA0400, an NCX inhibitor. The experimental protocol comprised 30 min of Mn(2+) perfusion (wash-in), followed by a 30-min wash-out period. There were three experimental groups: 1, NCX inhibition by 1 µ m SEA0400 during Mn(2+) wash-in only (SEAin, n=6); 2, NCX inhibition by 1 µ m SEA0400 during Mn(2+) wash-out only (SEAout, n=6); 3, no NCX inhibition during both wash-in and wash-out to serve as the control group (CNTL, n=5). Rapid T(1) mapping at a temporal resolution of 3 min was performed throughout the perfusion protocol using a triggered saturation-recovery Look-Locker sequence. Our results showed that NCX inhibition during Mn(2+) wash-in caused a significant increase in relaxation rate (R(1) ) at the end of Mn(2+) perfusion. During the wash-out period, NCX inhibition led to less reduction in R(1) . Further analysis of Mn(2+) content in myocardium with flame atomic absorption spectroscopy was consistent with the MRI findings. These results suggest that Mn(2+) accumulation and retention in rat hearts are, in part, dependent on NCX activity. Hence, MEMRI may provide an imaging method that is also sensitive to changes in NCX activity.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Ya
authors.initials: Y
authors.lastname: Chen
authors.forename: Kevin
authors.initials: K
authors.lastname: Payne
authors.forename: Vindya S
authors.initials: VS
authors.lastname: Perara
authors.forename: Songping
authors.initials: S
authors.lastname: Huang
authors.forename: Akemichi
authors.initials: A
authors.lastname: Baba
authors.forename: Toshio
authors.initials: T
authors.lastname: Matsuda
authors.forename: Xin
authors.initials: X
authors.lastname: Yu
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology*; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002469:Cell Separation; D006321:Heart / Q000187:drug effects* / Q000502:physiology*; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging; D008297:Male; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D010477:Perfusion; D010647:Phenyl Ethers / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors; D016276:Ventricular Function / Q000187:drug effects
chemical_list: D000814:Aniline Compounds; D010647:Phenyl Ethers; C430918:SEA 0400; D019831:Sodium-Calcium Exchanger; D008345:Manganese