Cellular toxicity of aminoglycoside antibiotics in G418-sensitive and -resistant LLC-PK1 cells.

The effects of gentamicin and G418 on the cellular function of LLC-PK1 epithelial pig kidney cells were investigated. Exposing the cells for 2 days to these aminoglycoside antibiotics inhibited the increase in cell-associated apical membrane enzyme activity (alkaline phosphatase, aminopeptidase, and gamma-glutamyltransferase). Kinetic analysis revealed that the maximal activity of alkaline phosphatase was reduced by these aminoglycosides. Both aminoglycosides inhibited [3H]leucine incorporation into microsomes prepared from LLC-PK1 cells. The LLC-PK1 cells transfected with DNA encoding aminoglycoside 3'-phosphotransferase II, designated T2000B, were resistant to G418 as assessed by colony formation assay and the number of floating dead cells and by assay of apical enzyme activity. After a 4-hr exposure to G418, [3H]leucine incorporation in the host LLC-PK1 cells was inhibited, whereas that in T2000B cells was relatively unaffected. Gentamicin inhibited [3H]leucine incorporation similarly in both cells. The inhibition of protein synthesis by aminoglycosides occurred earlier than that of apical enzyme activity. These findings suggest that the inhibition of protein synthesis by aminoglycoside antibiotics is a possible cause of the reduction in cell viability as well as the apical enzymes in LLC-PK1 cells.