COX-2 is rapidly induced by RANKL stimulation in a Rac1-dependent manner. (A) Expression of COX-2 mRNA in RAW264.7 and RAW-RacN17 cells stimulated with RANKL for the indicated periods was examined by Northern analysis. GAPDH was used as a control for total RNA loading. (B) Expression of COX-2 protein in RAW264.7 and RAW-RacN17 cells stimulated with RANKL for the indicated periods. Whole cell lysates (50 μg each) were immunoblotted with anti–COX-2 antibody and reprobed with antitubulin antibody.