ATP generation by normal chondrocytes treated with different nitric oxide (NO) donors. Articular chondrocytes were treated with 1 mM sodium nitroprusside (SNP) and 2 mM N-ethyl-2(1-ethyl-2 hydroxy-2-nitrosohydrazine (NOC-12) for 24 hours. Then the ATP assay was performed as described in Materials and methods. Values are the mean ± SD; n = 7. *P ≤ 0.05 versus untreated chondrocytes (control).