Figure 9

Comparable levels of extracellular signal-regulated kinase (ERK)1/2 phosphorylation are observed in chondrocytes treated with epidermal growth factor (EGF) alone or in combination with tumor necrosis factor alpha (TNF-α). Confluent monolayers of chondrocytes were treated for 4 hours with TNF-α (30 ng/ml) followed by (a) 15 min treatment or (b) 30 min treatment with EGF (10 ng/ml). Phosphorylation of ERK1/2 was determined by immunoblot assay using phospho-specific ERK1/2 antibody and ERK1 antibody (antibody against ERK1 is cross-reactive for ERK2). Blots shown are representative of three independent experiments.