Dose-dependent effect of SNP on cell viability in canine cruciate ligamentocytes. Cells were cultured with indicated concentrations of SNP (mM) for 18 h. Cell viability of (dark gray square) CCL and □ CaCL cells was measured by MTT assay and calculated with the formula reported in the M&M section. Control cells were not treated with SNP. The graphs data represent the mean ± SD from at least three separate experiments of four different cell donors, each performed in triplicates. * P < 0.05, ** P < 0.01 CCL vs. CaCL at each indicated concentration.