The depressant influence of extracellular fluid hyperoxia on liver slice oxygen uptake

The effect of oxygen tension (Po2) on oxygen consumption (Vo2) of rabbit liver slices was investigated to determine the relationship between extracellular fluid Po2 and liver slice Vo2. Seventy rabbits, 5 kg each, were sacrificed with air embolism. Liver slices (0.3 gm) in Krebs-Ringer's-phosphate (KRP) dextrose were placed in a constantly agitated, 37 degrees C, closed cuvette, and Po2 was continuously monitored down to 10 torr. The system was reoxygenated and closed, and observations were repeated. Hemoglobin concentration was measured on the liver slice homogenate, and a P50 was measured on autologous blood. The presence of small amounts of hemoglobin in the supernatant was confirmed by electrophoretic, spectrophotometric, and morphologic studies. The pH decreased from mean 7.47 to mean 7.37 during each run. The resultant increase in P50 was recalculated and included in the determination of each deltaO2 content/min (Vo2). Vo2 at Po2 30 torr was greater than Vo2 at Po2 90 torr (p less than 0.0001 in each case). Vo2 at Po2 30 torr was not significantly different in the first vs. the second run (p greater than 0.85). The critical oxygen tension for hepatocyte respiration appears to be 30 torr.