EVIDENCE FOR A NEGATIVE PASTEUR EFFECT IN ARTICULAR-CARTILAGE

Uptake of external glucose and production of lactate measured in fresh ly-excised bovine articular cartilage under O-2 concentrations ranging from 21% (air) to zero (N-2-bubbled). Anoxia (O-2 concentration <1% i n the gas phase) severely inhibited both glucose uptake and lactate pr oduction. The decrease in lactate formation correlated closely with th e decrease in glucose uptake, in a mole ratio of 2:1. This reduction i n the rate of glycolysis in anoxic conditions is seen as evidence of a negative Pasteur effect in bovine articular cartilage. Anoxia also su ppressed glycolysis in articular cartilage from horse, pig and sheep. Inhibitors acting on the glycolytic pathway (2-deoxy-D-glucose, iodoac etamide or fluoride) strongly decreased aerobic lactate production and ATP concentration, consistent with the belief that articular cartilag e obtains its principal supply of ATP from substrate-level phosphoryla tion in glycolysis. Azide or cyanide lowered the ATP concentration in aerobic cartilage to approximately the same extent as did anoxia but, because glycolysis (lactate production) was also inhibited by these tr eatments, the importance of any mitochondrial ATP production could not be assessed, A negative Pasteur effect would make chondrocytes partic ularly liable to suffer a shortage of energy under anoxic conditions. Incorporation of [S-35]sulphate into proteoglycan was severely curtail ed by treatments, such as anoxia, which decreased the intracellular co ncentration of ATP.