Aminoglycoside-induced alterations in apical membranes of kidney epithelial cell line (LLC-PK1)

Aminoglycoside-induced renal cell injury was investigated using the LLC-PK1 pig kidney epithelial cell line. The development of aminopeptidase and gamma-glutamyltransferase, marker enzymes for apical membranes, was inhibited in the LLC-PK1 cells cultured with gentamicin. The inhibitory effect of gentamicin on the enzyme activities was dose dependent and was related to its accumulation within the cells. The development of Na+ -dependent active transport of alpha-methyl-D-glucoside, a nonmetabolizable hexose, was also inhibited by treatment with gentamicin. Inhibitions in apical membrane enzyme activities and Na+ -dependent transport of alpha-methyl-D-glucoside were associated with the elevation of cytosolic free calcium, determined with a fluorescent indicator fura-2. The correlation between the alterations in apical membrane functions and the increase in cytosolic free calcium concentration was also supported by the study using the calcium ionophore A23187. The present data suggest that aminoglycoside-induced alterations in apical membranes of the LLC-PK1 cells are related to the increase in cytosolic free calcium levels.