Fig. 6. Effect of activation of RAW264.7 cells on the expression of HO-1, iNOS and the rate of respiration. (A) Cells that were activated for 12 hours in the presence or absence of L-NIO (500 µM) under ambient O₂ or hypoxic conditions expressed HO-1 and iNOS protein. Hypoxia itself induced HO-1 but not iNOS. (B) The respiration of activated cells was almost completely inhibited. Cells activated in the presence of L-NIO did not synthesise NO but still exhibited an inhibition of respiration that was increased by hypoxic incubation. n=3-4. ^**P<0.01 compared with control; ^*P<0.01 compared with respective L-NIO-treated controls; ^$P<0.01 compared with L-NIO-treated cells maintained at 21% O₂; ^#P<0.01 compared with cells activated in the presence of L-NIO at 21% O₂.