Phagocytosis of latex beads by rabbit retinal Müller (glial) cells in vitro.

The ability of rabbit retinal Müller (glial) cells to perform phagocytosis was studied in vitro. Müller cells were feed with various kinds of latex beads either shortly after enzymatical isolation from adult retinae or in monolayer cell cultures derived from neonatal retinae and kept 14 days in vitro. Both types of Müller cell preparations showed intense phagocytosis of latex beads. Moreover, when entire retinae were isolated and exposed (sclerad side up) to latex beads in vitro for 30 min, Müller cells had picked up fluorescent beads and showed, after fixation, intense labeling in radial sections of such retinae. Effective phagocytosis by Müller cells was demonstrated 1.) by transmission electron microscopy, 2.) by bright-field light microscopy of unstained large beads (diameter 660 nm), or 3.) by fluorescence microscopy of small (diameter about 60 nm) and large latex beads labeled with rhodamine. These results suggest that both labeled and unlabeled latex beads are suitable tools to study the phagocytotic activity of retinal glial cells in vitro, thus providing information on important processes occurring in situ during ontogenesis, physiological renewal of retinal receptor cells, and pathological events. We found that movements of cells or cytoplasmic excrescences, and cell-cell interactions, play important roles in removal of foreign particles out of the fluid environment. Engulfed latex beads move through the elongated cells with velocities similar to slow axoplasmic transport.