Release of PGE2 into culture medium following an impact load on articular cartilage explants. Explants of articular cartilage were impact loaded with a mass of 500 g dropped from 25 mm (0.13 J). The culture medium from each explant was collected at 3 days and 6 days following loading. The concentration of PGE2 in the medium was measured by ELISA, normalised to the wet weight of each explant and expressed per mg of cartilage. Day 6 results represent the cumulative release of PGE2 (combining the two 3-day periods). Mean values (± standard deviation, n = 3) from three experiments are shown. Each experiment used five replicates in each group. (a) Impact load significantly increased the concentration of PGE2 in the explant culture medium. Asterisks denote significant differences (*p ≤ 0.05, **p ≤ 0.01) between unloaded controls and impact loaded explants. (b) Celecoxib and indomethacin both reduced the release of PGE2 following an impact load. Asterisks denote significant differences (*p ≤ 0.05, **p ≤ 0.01) between impact loaded explants with no inhibitor added and impact loaded explants with inhibitor.