High-energy phosphates and function in isolated, working rabbit hearts

An isolated, working, rabbit heart has been developed for use with nuclear magnetic resonance (NMR) spectroscopy. This model is functionally stable over a 4-h period and displays classic hemodynamic responses to work-load changes. Control 31P spectra of this preparation (n = 5) were obtained with simultaneous recordings of left ventricular pressure (LVP), LVP differentiated with respect to time (dP/dt), heart rate (HR), and cardiac output (CO). ATP, phosphocreatine (PCr), and hemodynamics remained stable over a 90-min perfusion. Hearts were also subjected to 13.5 min of global ischemia (IS) at 37 degrees C followed by 60 min of reperfusion (RE, n = 7) or 45 min of chronic IS (n = 6). Contraction ceased within 60 s of IS. PCr loss was rapid, reaching undetectable limits by 11 min. ATP loss was gradual and bore no relationship to functional loss. ATP fell to 60 +/- 4% (means +/- SE) of pre-IS levels after 13.5 min of IS. With RE, PCr returned to control levels, whereas ATP values remained depressed for the entire 60 min. Functional activity resumed with RE, but dP/dt did not rise above 85 +/- 7% of preischemic values. No correlation between residual ATP at the end of IS and functional recovery during RE was evident.