Inhibition of gentamicin uptake into cultured mouse proximal tubule epithelial cells by L-lysine.
Gentamicin uptake and toxicity was studied in a nontransformed cell line obtained from the S1 segment of the proximal tubule epithelium of a transgenic mouse. Cytotoxicity was assayed using the dye 3-(4,-5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Gentamicin uptake was assayed by a fluorescence polarization assay. No differences in toxicity were found among cells incubated for 4 hours in complete culture medium, enriched Kreb's buffer alone, or enriched Krebs' buffer with added 300 micrograms/mL gentamicin, 0.5 mmol/L L-lysine, or gentamicin plus L-lysine. Uptake of 300 micrograms/mL gentamicin was minimal at zero time and increased as a function of time. Uptake of gentamicin at 4 hours was positively correlated with medium gentamicin concentration. Addition of 0.5 mmol/L L-lysine inhibited uptake of 300 micrograms/mL gentamicin 38.9 +/- 10.2%. No other amino acid, including D-lysine or arginine, significantly changed gentamicin uptake. The authors conclude that gentamicin and L-lysine share a specific uptake mechanism located in the apical membrane of renal proximal tubule cells.
Kaunitz
J D
JD
Research Service, Wadsworth Veterans Affairs Medical Center, Los Angeles, CA 90073.
Cummins
V P
VP
Mishler
D
D
Nagami
G T
GT
D000818:Animals; D002460:Cell Line; D004396:Coloring Agents; D003470:Culture Media; D004848:Epithelium; D005839:Gentamicins / Q000378:metabolism* / Q000633:toxicity; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D008239:Lysine / Q000494:pharmacology*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D013778:Tetrazolium Salts; D013844:Thiazoles
D004396:Coloring Agents; D003470:Culture Media; D005839:Gentamicins; D013778:Tetrazolium Salts; D013844:Thiazoles; C022616:thiazolyl blue; D008239:Lysine