The uptake and metabolism of fructose-1,6-diphosphate in rat cardiomyocytes

Fructose-1,6-diphosphate (FDP) is a glycolytic intermediate which has been theorized to increase the metabolic activity of ischemic tissues. Here we e xamine the effects of externally applied FDP on cardiomyocyte uptake and me tabolism. Adult rat cardiomyocytes were isolated and exposed to varying con centrations (0, 5, 25 and 50 mM) of FDP for either 1, 16 or 24 h of hypoxia (95% N-2/5% CO2), each time period followed by a 1 h reoxygenation (95% ai r/5% CO2). The uptake of FDP by rat cardiomyocytes was more concentration-d ependent than time-dependent. Furthermore, the uptake of FDP by the cardiom yocytes was similar in the hypoxia and normoxia treated cells. Alamar Blue, a redox indicator that is sensitive to metabolic activity, was used to mon itor the effects of the FDP on cardiomyocyte metabolism. In the 1 h hypoxia or normoxia group, the 5, 10 and 25 mM FDP showed a significant increase i n metabolism compared to the control cells. When the length of hypoxia was extended to 16 h, all doses of FDP were greater than control. And at the 24 h hypoxia or normoxia time period, only the 10, 25 and 50 mM FDP groups we re greater than control. The results indicate a non-linear trend between th e external concentration of FDP and the changes noted in metabolism. The fi ndings from this study indicate that a narrow concentration range between 5 -10 mM augments cardiomyocyte metabolism, but higher or lower doses may hav e little additional affect.