Effects of flow and energy metabolism on injury and Rb+ uptake in pig hearts: An Rb-87 and P-31 NMR study

In this work the roles of coronary flow (CF) and metabolism in Rb+ (K+ cong ener) uptake were studied. In isolated pig hearts the left anterior descend ing artery (LAD) was cannulated to maintain adequate perfusion of the LAD b ed. Rb+ loading was initiated and the LAD flow was either completely stoppe d (no flow (NF)) or reduced to 12% (low flow (LF)), or buffer was deoxygena ted without change in flow (hypoxic flow (HYP)) for 2 h. CF through the LAD was then restored to normal, or perfusion was switched to oxygenated buffe r. Serial Rb-87 MR images or localized P-31 spectra were acquired to compar e the Rb+ uptake and energetics in the left ventricular {LV) anterior (isch emic/hypoxic) and posterior (normal) walls. End-ischemic/ hypoxic Rb-87 sig nal intensities in the anterior wall were higher and the fluxes were greate r in the HYP and LF groups than in the NIF group. Phosphocreatine and ATP d ecreased less significantly and recovered better in the HYP and LF groups. Upon reperfusion/reoxygenation, the HYP and LF groups showed higher Rb-87 s ignal intensities and smaller or no infarctions in the anterior wall compar ed to those in the NF group. Ischemia reduces Rb+ uptake due to both flow l imitations and metabolic inhibition of cellular transport. Rb-87 MR1 has a potential for distinguishing necrotic and reversibly damaged tissue. (C) 20 01 Wiley-Liss, Inc.