Abstract
The relationships between pressure rate product (PRP) and flux (PCr→ATP) or flux (Pi→ATP) were studied in isolated perfused rat hearts by the saturation transfer method using 31P-NMR. The effects of propranolol and diltiazem on phosphate metabolism were also studied. After a 40 min preischemic period, the hearts were subjected to a 15 min period of ischemia, followed by 60 min of reperfusion. Propranolol (0.4-1.2μM) or diltiazem (3.0-6.0μM) was infused for 30 min before ischemia and reinfused after reperfusion for 60 min. The flux (PCr→ATP)/PRP ratio at reperfusion did not differ from that at preischemia. This value was also not affected by propranolol or diltiazem treatment. However, the flux (Pi→ATP)/PRP ratio at reperfusion was significantly less than that at preischemia. Moreover, this value was significantly improved by propranolol or diltiazem treatment. This study demonstrates that 1) flux (PCr→ATP) has a good correlation with cardiac performance, 2) stunned myocardium needs less ATP turnover for survival of its depressed contractile activity, and 3) flux (Pi→ATP) can limit recovery of postischemic performance. Protective effects of propranolol and diltiazem are exerted on the flux (Pi-ATP), i.e. ATP derived from glycolytic flux, in the reperfused heart.
