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The Journal of Cardiovascular Surgery 1999 August;40(4):481-6

Copyright © 2000 EDIZIONI MINERVA MEDICA

language: English

Effects of heat stress on metabolism of high-energy phosphates. Comparison of normothermic and hypothermic ischemia

Jayakumar J., Smolenski R. T., Gray C. C., Goodein A. T., Amrani M., Yacoub M. H.

From the Department of Cardiothoracic Surgery National Heart and Lung Institute Imperial College School of Medicine Harefield Hospital, Harefield, Middlesex, UK


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Back­ground. Alter­a­tions in meta­bolic path­ways may con­tribute to the car­di­op­ro­tec­tive ­effects of ­heat ­stress (HS). We inves­ti­gated the ­effects of HS on ATP and phos­pho­crea­tine (PCr) ­levels in the ­ischemic rat myo­car­dium, ­after ­both nor­mo­thermic and hypo­thermic ­ischemia.
­Methods. Two pro­to­cols ­were ­used: (1) nor­mo­thermic ­ischemia (20 min at 37°C) ­with no myo­car­dial pro­tec­tion (n=6 HS; n=6 con­trol); (2) hypo­thermic ­ischemia (4 hrs at 4°C) ­after car­di­o­plegic ­arrest (n=6 HS; n=6 con­trol). ATP and PCr ­levels in the ­heart ­were meas­ured ­using 31P ­nuclear mag­netic res­o­nance spec­tros­copy.
­Results. At the end of nor­mo­thermic ­ischemia, ATP ­levels ­were ­better main­tained in HS ­hearts (C vs HS: 4.51±0.66 vs 7.81±1.06 ­μmol/g dry wt±SEM, p=0.04). A ­trend for ­higher ATP con­tent in HS ­hearts was ­observed ­after 40 min of reper­fu­sion (C vs HS: 11.7±1.5 vs 16.9±2.0 ­μmol/g dry wt±SEM, p=0.09). PCr con­tent was ­also ­higher at the end of 40 min­utes of reper­fu­sion in HS ­hearts (C vs HS: 46.4±2.9 vs 56.9±3.0 ­μmol/g dry wt±SEM, p=0.03). ­After pro­longed hypo­thermic ­ischemia ­under car­di­o­plegic ­arrest, ­heat ­stress ­again led to ­better pres­er­va­tion of ATP ­levels at the end of ­ischemia (C vs HS: 5.71±0.88 vs 9.23±1.38 ­μmol/g dry ­wt±SEM, p=0.05) and ­after 40 min­utes of reper­fu­sion (C vs HS: 16.8±1.4 vs 24.6±2.8 ­μmol/g dry wt±SEM, p=0.03). PCr ­levels ­were ­also ­better main­tained at the end of ­ischemia (C vs HS: 4.87±0.77 vs 12.4±3.0 ­μmol/g dry wt±SEM, p=0.03) and ­after 40 min­utes of reper­fu­sion in HS ­hearts (C vs HS: 55.1±7.0 vs 79.8±7.3 ­μmol/g dry wt±SEM, p=0.03).
Con­clu­sions. ­Heat ­stress ­induces ­changes in the ­energy pro­file of the ­heart ­which ­results in ­better pres­er­va­tion of ATP and phos­pho­crea­tine ­levels. ­These ­changes ­could be ­observed ­after ­brief nor­mo­thermic ­ischemia and ­also ­after pro­longed hypo­thermic ­ischemia ­under car­di­o­plegic ­arrest, mim­icking con­di­tions of pres­er­va­tion for car­diac trans­plan­ta­tion.

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