Scanning electron microscopic study of lead effects on cerebral astrocytes in primary culture

The effects of lead acetate on the cell surface of primary cultured astrocytes from dissociated neonatal rat cerebrums were studied using scanning electron microscopy. Astrocytes, grown for two weeks in a modified Eagle's minimal essential medium containing 20% calf serum, were exposed to lead (1, 10, 30, 50, or 100 micrograms Pb/ml) for four days. Astrocytes grown in lead-free medium showed membrane folds (ruffles) and microvilli on the surfaces of perikarya. Vesicular structures or blebs (gliosomes) were scattered on the surfaces of perikarya and branched cell processes. Cultures exposed to 1 microgram Pb/ml were indistinguishable from controls. After exposure to 10 and 30 micrograms Pb/ml, microvilli disappeared, membrane folds were less extensive, and the number of surface blebs increased. Astrocytes exposed to 50 micrograms Pb/ml showed no surface membrane folds or microvilli while the blebs increased sufficiently to cover the surface of the perikarya. Cells treated with the highest lead concentration (100 micrograms/ml) were shrunken and perikarya again were covered with blebs. Transmission electron microscopy of the cells exposed to 10-100 micrograms Pb/ml showed membrane bound vacuoles and areas of cytoplasmic clearing, some of which may correspond to the surface blebs seen by SEM. These studies suggest that the changes in the cell surface resulting from lead exposure represent a toxic effect of lead on primary cultured astrocytes.