Figure 4. Inhibition or depletion of protein kinase C (PKCδ) prevented ethambutol (EMB)-induced suppression of the uptake of rod outer segments (ROS) in RPE50 cells. The phagocytosis assay was performed in RPE50. In (A) the fluorescein isothiocyanate (FITC)-labeled ROS were added to the cells in the absence (con) or presence of EMB alone, or EMB plus various PKC isozymes (as indicated) for 2.5 h. In (B), the cells were untransfected (con), transfected with shRNA of control (lamin), or various PKC isozymes for 36 h, followed by the addition of the FITC-labeled ROS added in the absence (CON) or presence of EMB for 2.5 h. The FITC-labeled ROS (green dot) up-take by the cells was observed under a phase contrast microscope (200× magnification). The nuclei were stained with PI (red) as counterstaining. The figures shown are representative of six to eight repeated experiments. (C) and (D) exhibit quantitative data for (A) and (B), respectively. The extent of ROS uptake was expressed as ROS/cell obtained from the average of the number of ROS and the cells in eight fields, under a phase contrast microscope. The asterisks (* and **) indicate statistical significance (p<0.05 and p<0.005, respectively, n=7) between the indicated groups.