Figure 1.

ATRA upregulates COX-1 and COX-2 protein expression and increases PGE₂ production in MC (a, b). Expression of COX-1 and COX-2 proteins was analysed by Western blot in MC (a) incubated for 24 h with the indicated concentrations of ATRA or (b) incubated with 10 μM ATRA for the indicated times. Equal protein loading was confirmed by probing with an anti-α-actin antibody. Normalized density ratio of either COX-2 or COX-1 over α-actin is indicated for each band. Each photograph represents at least three repeated experiments. (c) PGE₂ production in MC incubated for 24 h with 10 μM ATRA. PGE₂ in the medium was determined in triplicate in four separate experiments. For comparison, the effects of 10 ng ml⁻¹ IL-1β on PGE₂ production as well as on the expression of COX-1 and COX-2 (inset) were analysed in parallel. ^*P<0.01 vs control.