Adenosine Receptor Blockade Increases Lactate and Purine Release But Does Not Affect Functional Recovery in Isolated Rabbit Myocardium

Abstract

Wang, Sheng, Adenosine Receptor Blockade Increases Lactate and Purine Release but does not Affect Functional Recovery in Isolated Rabbit Myocardium Master of Science (Biomedical Sciences), December 1995; 67 pp; 3 tables; 8 figures; bibliography, 121 titles. This study tests the hypothesis that endogenous adenosine mediates recovery of cardiac function in ischemia/reperfused rabbit hearts. Isolated isovolumic rabbit hearts perfused at constant pressure was subjected to mild ischemia (perfusion pressure 50 cm H2) or moderate ischemia (perfusion pressure 30 cm H2O) for 90 min followed by 60 min of reperfusion. In treated hearts, infusion of 100 μM 8-p-sulfophenyl theophylline (SPT) was initiated 20 min before ischemia and maintained throughout the experiment. Adenosine receptor blockade did not affect left ventricular function assessed from pressure-heart rate product (PRP). Lactate release increased to 152 ± 24% of baseline during mild ischemia and 259 ± 26% of baseline during moderate ischemia in untreated hearts. Lactate release was markedly elevated at baseline, ischemia and reperfusion by SPT treatment (p [less than] 0.05 compared to untreated). Purine nucleoside release was 4.1 ±0.7 nmol · min-1 · g-1 in SPT treated group and 1.8 ± 0.24 nmol · min-1 · g-1 in untreated group during moderate ischemia (P [less than] 0.05). Myocardial efficiency was significantly lower in the SPT treated hearts (240 ± 11 mmHg · g=1 · μl-1 O2) compared to untreated hearts (300 ± 22 mmHg · g-1 · μl-1 O2) during reperfusion after moderate ischemia. In conclusion, adenosine receptor blockade stimulates glycolysis in normoxic and ischemic myocardium, but does not affect post-ischemic functional recovery.