We report morphologic and viability changes in the rabbit corneal epithelium exposed in vitro to gentamicin sulfate. Rabbit corneal epithelial cells (3 x 105) were seeded in replicate 24-well plates at their first in vitro passage, and gentamicin in concentrations of 0, 50, 250, 500, 1,000, or 5,000 μg/ml was added to the tissue culture medium beginning 7 days after subculture. By phase contrast microscopy, changes in cell morphologic appearance, particularly increased cytoplasmic granularity, were observed in the 5,000-μg/ml groups as early as 24 h after introduction of the drug. At 48 h, similar findings were observed in the 250-μg/ml group and at all higher concentrations. The cytoplasmic granularity was not noted in the 0- or 50-μg/ml groups. By electron microscopy, these observations correlated with ultrastructural findings of increased accumulations of intralysosomal bodies beginning in the 250-μg/ml group after 48 h of exposure to gentamicin. Furthermore, a statistically significant difference (p = 0.001) was demonstrated between the total number of viable cells in the low-dose group (50-μg/ml) and the high-dose groups (≥250-μg/ml) for exposure periods of 48 h or more. These findings demonstrate aminoglycoside toxicity to corneal epithelial cells in vitro, similar to that seen in the human kidney and conjunctiva.
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