PORCINE IRIS PIGMENT EPITHELIAL-CELLS CAN TAKE UP RETINAL OUTER SEGMENTS

This study investigates the ability of iris epithelial cells (IPE) to ingest rod outer segments (ROS) and compares the amount of phagocytosi s of porcine RPE and IPE cells by the use of a pH sensitive fluorescen t dye (carboxy SNAFL) at the light microscopic level. The dye allowed investigation of ingestion separately from binding of rod outer segmen ts. In a second set of experiments, after exposing ferritin-labeled RO S to the cultured cells, phagosomes were also counted in electron micr oscopic sections. Additionally immunocytochemical staining was perform ed with IPE and RPE cells. Both cell types stained positive with polyc lonal NaK-ATPase antibodies against the alpha 1 subunit from rat brain and kidney. The epithelial nature of the cultured cells was determine d by monoclonal anti-human-cytokeratin antibodies. Moreover, the ultra structure of the cells revealed high amounts of phagosomes smaller tha n 1 mu m in diameter present in both RPE and IPE cells. The iron label of the phagosomes was determined by EELS spectra taken from individua l phagosomes. Electron and light microscopic quantification shows that cultured IPE cells have 64% of the phagocytic capacity of the RPE wit h respect to phagosomes larger than 1 mu m in diameter. (C) 1997 Acade mic Press Limited.