Effects of H₂O₂ on cell viability and senescence.

<p><b>a.</b> Cell viability was assessed by alamar blue fluorescence (Ex 530, Em. 590 nm) 16 hr after the addition of H₂O₂ at the indicated concentrations (n = 6, ** p<0.01). Incubation with H₂O₂ at concentrations between 50–250 µM progressively decreased cell viability. <b>b.</b> SA-galactosidase (SA-Gal) activity. Cells were incubated in media containing the indicated concentration of H₂O₂ for 2 hr. They were then incubated in the same medium without H₂O₂ for 3–4 days, after which they were stained for SA-Gal. H₂O₂ increased the number of positive cells. <b>c.</b> Percentage of positive cells was increased approximately 3-fold by prior incubation with 50 or 100 µM H₂O₂. In excess of 300 cells were counted for each condition. (n = 3–6, ** p<0.01) <b>d.</b> Time course of appearance of SA-galactosidase positive cells after treatment with 50 µM H₂O₂.