Fructose-1,6-bisphosphate enhances hypothermic preservation of cardiac myocytes.

Background: Previous studies from our project found that fructose-1,6-bisphosphate (FBP) enhanced the functional recovery of animal hearts after hypothermic preservation, and that rat cardiac myocytes take up FBP at 3 degrees C. In this study we tested the effects of FBP, as well as other compounds related to glycolysis and pyruvate oxidation, on the hypothermic preservation of myocytes.

Methods: Isolated myocytes were incubated in ischemic suspensions at 3 degrees C, and aliquots examined over 72 hours for retention of rod-shaped morphology. In some experiments adenine nucleotide levels were measured by high-performance liquid chromatography (HPLC).

Results: FBP at 1 to 10 mmol/liter markedly reduced the death rate (65% reduction at 5 mmol/liter). Glucose at 2 to 10 mmol/liter was less beneficial (20% reduction). Insulin increased the death rate by about 25% when present alone, and it did not enhance the beneficial effects of FBP or glucose. Dichloroacetate (DCA), which stimulates pyruvate dehydrogenase, had little effect at 0.5 to 10 mmol/liter. Glucose and DCA did not increase the beneficial effects of FBP. After 6 to 24 hours of hypothermia, FBP- and glucose-treated cells had 25% to 50% higher ATP levels and 10% to 20% higher ATP:ADP ratios than untreated cells. Effects of FBP on preservation of morphology were much greater than effects on ATP levels.

Conclusions: The results suggest that the effects of FBP and glucose were through glycolytic ATP production rather than through sugar oxidation via pyruvate dehydrogenase. The divergence in effects on preservation and effects on ATP suggests a role for a sub-cellular compartment of ATP in preservation.