Authors : Koichi Kawahara , Hiroyuki Kimura and Yoshiko Yamauchi
Abstract: Ventricular Fibrillation (VF) is known to alter myocardial energetics, but the mechanism of these changes has not been fully elucidated. We have recently demonstrated that the perfusion of isolated hearts with Ruthenium Red (RR), a blocker of the mitochondrial Ca2+ uniporter, converted pacing-induced sustained VF to Ventricular Tachycardia (VT). Here we investigated whether and if so how perfusion of the heart with RR during normal beating and during sustained VF changed the myocardial energetics. Phosphorus nuclear magnetic resonance spectroscopy and magnetization transfer ( P NMR) were applied to isolated perfused rat 31 hearts. Sustained VF was induced by burst pacing of the heart. In hearts beating normally, perfusion with RR (10 ?M) significantly reduced Left Ventricular Developed Pressure (LVDP) and isovolumic contractile performance (expressed as the product of heart rate and LVDP). However, the amounts of Creatine Phosphate (CrP), ATP and their sum (CrP+ATP) did not significantly change as compared with those before the perfusion, suggesting that there existed a close balance between energy supply and demand during perfusion with RR. In contrast, during pacing-induced sustained VF, RR perfusion resulted in a decrease of inorganic phosphate (Pi) and in an increase of both CrP and ATP as compared with levels during sustained VF, although the RR-induced changes were not significant. In addition, RR perfusion increased the sum of high-energy phosphate compounds; that is, CrP+ATP, to almost the same level as that in hearts beating normally. This study demonstrated that the perfusion of isolated rat hearts with a blocker of the uptake of Ca2+ by mitochondria during sustained VF resulted in the close balance between myocardial energy supply and demand, suggesting that the balance was lost during VF and RR perfusion significantly ameliorated this imbalance.
Koichi Kawahara , Hiroyuki Kimura and Yoshiko Yamauchi , 2005. Ruthenium Red-induced Changes in Myocardial Energetics During Normal Beat and Ventricular Fibrillation in Isolated Rat Hearts . The Cardiology, 1: 95-101.