Quantitative assay of phagocytosis by retinal pigment epithelium: an organ culture model

The purpose of the study was to develop a model for quantitative analysis of phagocytosis by retinal pigment epithelium (RPE). The posterior segment of the bovine eye, devoid of the neural retina and vitreous humour, formed a hollowed cup. RPE lining the interior of the cup (RPE cup) was incubated as an organ culture at 37°C for 24 hr, with latex particles (1·09 μm) previously coated with 125I-labelled γ-globulin and then thoroughly washed. The amount of radioactivity per RPE cup was related to the phagocytic activity of the RPE cells. Electron microscopy verified that the particles were indeed internalized by RPE. Phagocytosis was significantly inhibited ( P < 0·005) by iodoacetate (10 −3 m), colchicine (10 −4 m) and cytochalasin B (10 μg/ml). Dibutyryl c′AMP (10 −3 m) and bromo-c′GMP (10 −3 m) did not have any significant effect on phagocytosis.