TRANSPORT OF GENTAMICIN AND FLUID-PHASE ENDOCYTOSIS MARKERS IN THE LLC-PK1 KIDNEY EPITHELIAL-CELL LINE

In order to characterize the transport of aminoglycoside in the cultur ed kidney epithelial cell line LLC-PK1, cellular uptake of gentamicin was studied in comparison with those of fluid-phase endocytosis marker s, lucifer yellow and horseradish peroxidase. The uptake of gentamicin and fluid-phase markers were time-dependent and were reduced at low t emperature. The rate of gentamicin uptake was, however, faster than th ose of lucifer yellow and horseradish peroxidase, and was saturable. T he accumulation of gentamicin in the cells was increasing even after 6 days of incubation, whereas that of lucifer yellow reached a steady s tate by 1 day. Release of intracellular gentamicin from LLC-PK1 cells was much slower than that of lucifer yellow. Gentamicin uptake, but no t lucifer yellow uptake, was increased by reducing the ambient ionic s trength. Under the low ionic strength conditions, gentamicin uptake wa s inhibited by the presence of other aminoglycosides, lysozyme, polyam ines such as spermine and inorganic cations such as calcium. These res ults indicate that gentamicin electrostatically binds to the cell apic al membrane and is subsequently taken up by an adsorptive endocytosis in LLC-PK1 cells.