Uptake of Doxorubicin by Cultured Kidney Epithelial Cells LLC-PK₁

Abstract

The renal handling of doxorubicin (DXR) was investigated using a kidney epithelial cell line, LLC-PK₁. The uptake of DXR by LLC-PK₁ cells cultured on plastic dishes was shown to be temperature and concentration dependent. The initial uptake of DXR was slightly saturable. The K_m and V_max of the saturable component were calculated to be 20.2 μM, and 0.355 nmol/mg protein/10 min, respectively. The release of DXR from LLC-PK₁ cells was very slow at 37°C and almost negligible at 4°C, indicating that most of the DXR in the cells irreversibly binds to cellular constituents and that only a slight amount of unbound DXR participates in the efflux out of the cells. DXR uptake at 37°C was significantly decreased in the presence of 2, 4-dinitrophenol. However, organic cations and aminoglycoside antibiotics, such as tetraethylammonium, N¹-methylnicotinamide, guanidine, gentamicin and neomycin, did not inhibit DXR uptake, suggesting that a process distinct from the organic cation transport system and absorptive endocytosis might be involved in the uptake of DXR by LLC-PK₁ cells.