Differential uptake of dextran beads by astrocytes, macrophages and oligodendrocytes in mixed glial-cell cultures from brains of neonatal rats.

The present study addresses a controversy over the abilities of astrocytes to perform phagocytosis. Primary glial-cell cultures were prepared from the brains of neonatal rats and were incubated with fluorescently-labeled dextran beads (molecular weights approximately 10 and approximately 40 kDa). Astrocytes and oligodendrocytes were double-labeled by immunofluorescence staining of cell-specific markers, and microglia by lectin histochemistry. Cells were permitted to take up beads for 1 h, fixed, and incubated with primary antibodies, followed by fluorescent secondary antibodies or fluorescently-labeled lectin. Macrophages and astrocytes internalized beads of both sizes. In astrocyte processes the beads appeared to line up along glial filaments. The results, which provide direct evidence for uptake of beads by astrocytes in vitro and against equally rapid, if any, uptake by oligodendrocytes, bear upon issues of acid/base balance and glial cell development and are relevant to neuropathological observations in human disease.