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Figure 4: Effects of PFOS on ERK activation in SH-SY5Y cells. (a) ERK1 and ERK2 mRNA levels in SH-SY5Y cells. (b) ERK and pERK protein levels and the pERK/ERK ratio in SH-SY5Y cells; the band intensities of pERK and ERK were quantified, and the fold increases in the ratio of pERK/ERK are presented as a bar graph. (c) The protein levels of ERK1/2 and pERK1/2 were determined by Western blot analysis using β-Actin as an internal control. Each data point was normalized to the control (DMSO), and the data are presented as mean ± SD from three independent experiments. , experimental values compared with control values.