Effects of colchicine on phagosome-lysosome interaction in retinal pigment epithelium. II. In vitro observations on histio-organotypical retinal pigment epithelial cells of the pig (a preliminary report).

Phagocytic activity of histiotypical and organotypical retinal pigment epithelial cells was studied by SEM and EM. After a latent period polystyrene microspheres of different diameter were captured by newly formed microvilli. No mechanism of discrimination according to the size of microspheres was observed. After engulfment, microvilli of histiotypical cells decreased in length and finally disappeared. Lysosomes increased in number when compared to unstimulated cells and fused with many latex-containing phagosomes. Colchicine, when added at 5 X 10(-5) M to the medium, inhibits phagosome-lysome interaction, thus confirming in vivo observations.