Effects of HIV-1 Tat on ERK Phosphorylation in RPE. (a): ERK1/2 phosphorylation was determined using an antibody specific to phospho-ERK1/2 after incubation of D407 with 100 nM HIV -1 Tat and Hi-Tat for various times, as indicated. Equal loading of protein was monitored using a specific antibody to total ERK. (b): Results of scanning densitometry of the exposed films. Data are expressed as arbitrary units of intensity relative to the control value, and are the mean ± S.D. of 3 independent experiments (*P < 0.05).