The Oxidation of Exogenously Added Organic Anions by Platelets FacilitatesMaintenance of pH During Their Storage for Transfusion at 22°C

Abstract

Previous studies of platelet metabolism during the storage of platelet concentrates (PCs) at 22 degrees C for transfusion have shown high rates of both oxygen consumption and aerobic glycolysis with little oxidation of pyruvate produced by glycolysis. During storage in plasma, free fatty acids are major oxidative fuels. Glutamine is also present as a potential fuel but relatively little is metabolized beyond glutamate. In synthetic media, acetate is oxidized and provides a poorly understood buffering function. In the current work, acetate and pyruvate (6 to 25 mmol/L, sometimes with their 14-C-labeled counterparts) were added to PCs stored in plasma. They were both vigorously metabolized, predominantly to CO2 (0.51 +/- 0.08 and 0.31 +/- 0.06 mmol/d/10(12) platelets for acetate and pyruvate, respectively). The metabolism of these exogenous substrates was associated with significantly increased oxygen consumption and decreased glucose consumption, fatty acid oxidation, and bicarbonate utilization for buffering. In a more limited number of studies, similar findings were observed with addition of beta-hydroxy-butyrate. Superior maintenance of pH in the presence of these additives could be attributed to the fact that the metabolism of an organic anion requires that a proton be brought with the anion into the metabolic pathway, thus providing an alkalinizing effect. Pyruvate (but not acetate) also stimulated the metabolism of glutamate. Studies with 14-C-labeled glucose suggested significant activity of the hexose-monophosphate shunt during PC storage and confirmed that little, if any, pyruvate derived from glucose was fully oxidized. Taken together, the results provide a relatively complete picture of the pathways of energy metabolism used by platelets during PC storage and suggest a strategy by which organic anions such as acetate can be used to improve the results of such storage.