Time course of the expression of prostaglandin E synthase (PGES) and cyclooxygenase (COX) isoenzymes in chondrocytes stimulated with interleukin-1β (IL-1β). Chondrocytes from osteoarthritis patients were incubated with IL-1β (1 ng/ml) for the indicated durations. (a) Total RNA from the cells was subjected to Northern blot analysis for membrane-associated PGES-1 (mPGES-1), cytosolic PGES (cPGES), COX-1, COX-2, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). (b) Protein from the cells was subjected to Western blot analysis for mPGES-1, cPGES, COX-1, and COX-2. Representative results from three patients are shown here.