Effect of DPI (10 μM), apocynin (1 μM), aspirin (100 μM), allopurinol (100 μM) or rotenone (10 μM) on prednisolone (1 μM)-stimulated O2•− formation by PAECs following a 16-h incubation. Data=mean±s.e.m.; n=6. *P<0.05, comparing prednisolone-induced levels to control in the absence of inhibitors. $P<0.05, significantly inhibited compared to prednisolone-treated cells.