Abnormal organelles in cultured astrocytes are largely enhanced by streptomycin and intensively by gentamicin

The effects of two aminoglycoside antibiotics on cultured astrocyte organelles were investigated in rat, sheep, and human cultured astrocytes using transmission electron microscopy. Marked changes in mitochondrial shapes were observed in cultured or subcultured astrocytes obtained from three species, including humans. As well, new types of organelles were observed: (i) numerous concentric membranes forming vesicles, which were termed multilamellar vesicles; and (ii) many vesicles gathering into membranous structures, which were termed multivesicular myeloid bodies. The number of abnormalities increased proportionally with increasing concentrations of the two aminoglycosides (streptomycin and gentamicin). The incorporation of peroxidase or albumin–gold complex in the abnormal vesicles showed that the endolysosomal system was involved in the formation of these vesicles. Our results show that: abnormal organelles are present in cultured astrocytes; these abnormalities are enhanced by streptomycin and gentamicin; and gentamicin induces more abnormalities than streptomycin. The binding of aminoglycosides to membrane phospholipids may explain the formation of the observed abnormalities in rat, sheep, and human cultured astrocytes.