FIGURE 6.

Cell survival effects of PEDF on R28 cells. A, kinetics of PEDF cell survival activity with increasing concentrations of PEDF using a real-time microelectronic cell sensor system. Cells were plated in duplicates, and after 8 h, serum-containing medium was replaced with serum-free medium containing increasing concentrations of PEDF (as indicated). Cell index was monitored each hour for 48 h. Cell index values were averaged. Data were plotted with cell index ± S.D. (error bars) as a function of time. The arrow indicates the time at which PEDF was added. B, the plot of cell index value at the end point as a function of PEDF concentration was obtained using GraphPad Prism with an equation for dose-response-stimulation (log[agonist] versus response). The calculated half-maximal response was EC₅₀ = 2.233 ± 1.873 nm (see inset). Each point is the average of duplicate wells ± S.D. C, relative cell numbers were determined at the end point using intracellular ATP as a live cell biomarker. A plot of relative cell numbers as a function of PEDF concentration was obtained using GraphPad Prism as in B. The calculated half-maximal response was EC₅₀ = 3.29 ± 1.98 nm (see inset). Each point is the average of duplicate wells ± S.D.