Stimulation of NO production and induction of iNOS mRNA expression by OCP crystals. Nonadherent bovine articular chondrocytes were stimulated with OCP crystals (0.5 mg/ml) or IL-1β (10 ng/ml). (a) iNOS and collagen II transcripts were detected in cell pellets by RT-PCR (see Materials and method). (b) Absorbance ratio (iNOS/GAPDH) of the RT-PCR. The RT-PCR was representative of three independent experiments, while NO release (triplicate experiments) and the absorbance ratio were expressed as mean ± standard deviation from the same three experiments. *P < 0.05, **P < 0.01, OCP versus control. GAPDH, glyceraldehyde-3-phosphate dehydrogenase; iNOS, inducible nitric oxide synthase; OCP, octacalcium phosphate.