Figure 1. Protein kinase C (PKC)δ was required for ethambutol (EMB)-induced vacuolar formation in retinal pigment epithelium (RPE). RPE50 (A) or ARPE19 (C) cells were untreated (denoted as C), treated with 8.0 mM EMB alone, or EMB plus the indicated inhibitors of PKC isozymes for 24 h. Pictures were taken under a phase contrast microscope with 200× magnification. This result is representative of three reproducible experiments. (B) and (D) are quantitations of cytoplasmic vacuolization for (A) and (C), respectively, performed as described in Methods. The number of vacuoles/per field were compared between indicated treatment groups using one way ANOVA followed by Dunnett’s post hoc tests. The asterisks (* and **) indicate statistical significance (p<0.05 and p<0.005, respectively, n=3) between the indicated groups.