Temperature Threshold and Modulation of Energy Metabolism in the Cardioplegic Arrested Rabbit Heart

• Published in: Cryobiology Vol. 36; no. 1; pp. 2 - 11
• Main Authors: Ning, Xue-Han, Xu, Cheng-Su, Song, Ying C., Childs, Keith F., Xiao, Yun, Bolling, Steven F., Lupinetti, Flavian Mark, Portman, Michael A.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.02.1998; Elsevier
• Subjects: Adenosine Triphosphate - metabolism; Aerobiosis; Anaerobiosis; Animals; ATP; Biological and medical sciences; cardioplegia; CO2; Energy Metabolism; Female; Fundamental and applied biological sciences. Psychology; glucose; Glucose - metabolism; Heart - physiology; Heart Arrest, Induced; Hemodynamics; hypothermia; In Vitro Techniques; Intermediate and energetic metabolism; lactate; Male; Metabolisms and neurohumoral controls; Myocardial Contraction; myocardial ischemia; Myocardial Ischemia - metabolism; Myocardial Ischemia - physiopathology; myocardial reperfusion; Myocardial Reperfusion Injury - metabolism; Myocardial Reperfusion Injury - physiopathology; Myocardial Reperfusion Injury - prevention & control; Myocardium - metabolism; Perfusion; Rabbits; Temperature; threshold; Vertebrates: anatomy and physiology, studies on body, several organs or systems; glucose; cardioplegia; hypothermia; myocardial reperfusion; CO2; temperature; myocardial ischemia; threshold; lactate; ATP; Heart; Cardioplegic solution; Vertebrata; Energy metabolism; Temperature; Mammalia; Rabbit; Environmental factor; Lagomorpha; Isolated organ
• ISSN: 0011-2240; 1090-2392
• DOI: 10.1006/cryo.1997.2054

Hypothermia protects ischemic tissues by reducing ATP utilization and accumulation of harmful metabolites. However, it also reduces ATP production, which might cause deterioration in the energy supply/demand ratio. Modulation of energy supply/demand according to temperature has not been previously studied in detail. In this study, isolated, perfused rabbit hearts (n= 60) were used to determine the effects of various temperatures on myocardial energy metabolism and function during cardioplegic arrest. Ischemia was induced by crystalloid cardioplegic solution at 4, 18, 30, and 34°C for 120 min, respectively. At each temperature, the hearts were divided into a glucose-treated group which contained 22 mM glucose in cardioplegic solution as the only substrate and a control group which contained 22 mM mannitol to keep same osmolarity. Following 15 min reperfusion, recovery of left ventricular developed pressure (DP), ±dP/dtmax, and the product of heart rate and DP were significantly higher in 30, 18, and 4°C groups than those in 34°C control group. The functional recovery was also significantly higher in the 34°C glucose-treated group than that in the 34°C control group, but there was no difference between those groups at 30°C and the temperature below 30°C. Myocardial ATP concentration was significantly lower in 34°C control group than those in other groups. There is a close relationship between myocardial ATP concentration and functional recovery (R2= 0.90). The accumulations of lactate and CO2were significantly higher at 34°C in glucose-treated group than those in the control group. However, there was no significant difference between these two groups at 30°C and the temperature below 30°C. These results indicate that under these study conditions: (1) a marked decrease in energy supply/demand occurs above 30°C, implying that a temperature threshold exists; and (2) this can be ameliorated by provision of glucose as substrate in cardioplegia solution.