The fuel of the spleen. Studies using a new method for perfusing the rat spleen with whole blood.

1. An improved rat spleen perfusion is described incorporating a method of defibrination which avoids the use of heparin and enables the spleen to be perfused with rat blood for several hours at a haematocrit of 40% and for 12 h or more at a haematocrit of 20%. 2. Glucose oxidation accounted for 11.6% of the total oxygen consumption but this represented only 8% of total glucose uptake, which was largely converted to lactate and released into the perfusate. However, significant amounts of lactate were oxidized. These results can be explained by the presence of at least two cell populations, one emphasizing the anaerobic oxidation of glucose and the other aerobic metabolism, particularly of lactate. 3. Non-esterified fatty acid and 3-hydroxybutyrate, when available at physiological concentrations, were shown to be major oxidative fuels of the spleen. 4. Chylomicron triacylglycerol was hydrolysed readily and taken up, but not oxidized extensively.