HYPOTHERMIC PRESERVATION OF THE RAT-HEART - COMPARISON OF IMMERSION AND LOW-FLOW PERFUSION METHODS - CONTRIBUTION OF P-31-NMR SPECTROSCOPY

Comparison of rat heart preservation by simple storage in a cardioplegic solution at 4 °C (6 hr for group I; 15 hr for group II) and by hypothermic low-flow perfusion of the same solution (0.3 ml min-1, 15 hr: group III) was performed by measuring biochemical and functional parameters and by collecting 31P-NMR Spectroscopy data. When compared to control values, adenine nucleotide levels remained unchanged in group I hearts, while glycogen was 45% hydrolyzed and lactate level increased by 700%. Extension of heart immersion to 15 hr (group II) led to breakdown of ATP (- 77%), of the sum of adenine nucleotides (- 27%), and of glycogen (- 77%), whereas lactate accumulation reached 900% of the control value. Functional recovery, measured at the end of a 60-min reperfusion was less than 10% in group II hearts when compared to group I hearts. This dramatic development was completely avoided by hypothermic low-flow perfusion (group III). 31P-NMR data showed that phosphocreatine was completely degraded in all groups of preserved hearts. Low-flow perfusion limited cellular acidosis. The ATP Pi (Pi = inorganic phosphate) ratio calculated from NMR data was lower for group II hearts (0.04 ± 0.01, n = 6) than for group I hearts (0.29 ± 0.12; n = 6) or group III hearts (0.19 ± 0.09; n = 6) and could constitute a convenient bioenergetic index to predict the capability of the heart to recover satisfactory contractility following a preservation period. © 1990.