Dissociation of adenosine triphosphate levels and contractile function in isovolumic hearts perfused with...

Addition of 2-deoxyglucose (DG, 8 to 13 mM) to a perfusate containing 5 mM pyruvate as oxidizable substrate caused gradual decline of contractile function of Langendorff-perfused isovolumic rat heart. Simultaneously 31P-NMR spectra showed accumulation of 2-deoxyglucose-6-phosphate (DG-6P) and decrease in phosphocreatine (PCr) and ATP contents; inosine appeared in high concentration in perfusate leaving heart. Subsequent reperfusion of the heart with DG-free solution resulted in the recovery of contractile function and PCr (to 75%), as well as in slow decay of DG-6P at unchanged low level of ATP (35%). No correlation was found between tissue ATP content and contractile function, when expressed as the product of developed pressure and heart rate. In contrast, contraction correlated with tissue PCr level at low ATP. These data demonstrate that effective contraction of the isovolumic heart is possible at substantially decreased level of cytoplasmic ATP. The results of this study are in accord with a concept of ATP compartmentation in cardiac cells.