Differences in fuel utilization between trout and human thrombocytes in physiological media

Cell culture preparations now play a significant and essential role in physiological and biochemical studies of cell biology. However, the fuels offered in cell culture media are only glucose and glutamine, plus whatever might be in the added sera. It is currently difficult to find a rational way forward on this problem, as there are few data on what fuels cells use in vivo or even in an in vitro physiological situation. A recent study on human platelets redressed the situation somewhat by finding that 75% of ATP turnover could be accounted for by aerobic glycolysis, and by the oxidation of glucose, hydroxybutyrate, acetate, glutamine, palmitate and oleate. In the present study we used a similar strategy to investigate fuel choices by trout thymocytes, cells with a similar function but from a different phylogenetic group. When these cells were presented with a physiological medium, we found that aerobic glycolysis accounted for 9% of total ATP turnover, glucose and glutamine oxidation made a combined contribution of 2.3%, oleate and palmitate oxidation accounted for 15%, and 74% was unaccounted for. These patterns of fuel use are very different from that in human platelets. They demonstrate the cell- and animal-specific nature of cellular metabolism and again expose the inadequacy of the fuel component in culture media.