Phospholipid peroxidation in isolated perfused rat hearts subjected to hypothermia followed by rewarming: inverse relation to loss of function.

In the present experimental study phospholipid peroxidation after hypothermia and rewarming was investigated in isolated buffer-perfused rat hearts. Stable normotherm perfusion (37 degrees C) for 20 min was followed by cooling to 14 degrees C, 4 h perfusion at 14 degrees C, and rewarming to 37 degrees C followed by 30 min normotherm perfusion. Seven hearts went through the whole protocol, whereas six hearts were subjected only to the initial stabilization period. Mechanical performance was measured by a balloon in the left ventricle (LV) permitting measurements of LV pressure and its derivatives. At the end of perfusion, hearts were freeze clamped in liquid nitrogen for phospholipid peroxidation measurements, phospholipid fatty acid composition, high-energy phosphate content (adenosine tri-, di-, and monophosphate and creatine phosphate), and tissue water content. After rewarming there was a significant reduction in mechanical performance and coronary flow. Tissue content of high-energy phosphates was decreased and tissue water content was increased. Levels of peroxidized polyunsaturated fatty acids (conjugated diens) in phospholipids and nonesterified fatty acids were not significantly changed (135.2 +/- 31.1 vs 74.3 +/- 7.6 nmol/g tissue dry wt and 1212 +/- 203 and 1685 +/- 197 nmol/g in control and rewarmed hearts. However, the amount of peroxidized polyunsaturated fatty acids in phospholipids expressed as a fraction of the phospholipids was significantly reduced by the cooling/rewarming procedure (1.28 +/- 0.22 vs 0.61 +/- 0.09 x 10(-3), P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)