Transcellular transport of creatinine in renal tubular epithelial cell line LLC-PK1.

BACKGROUND/AIM: Creatinine is excreted into urine via tubular secretion in addition to glomerular filtration. In the present study, characteristics of the creatinine transport in renal epithelial cells were investigated. METHODS: The transcellular transport and accumulation of [14C]creatinine and [14C]tetraethylammonium (TEA) were assessed using LLC-PK1 cell monolayers cultured on porous membrane filters. RESULTS: [14C]Creatinine was transported directionally from the basolateral to apical side of LLC-PK1 cell monolayers. Basolateral uptake of [14C]creatinine was dependent on membrane potential, and was saturable with apparent K(m) and V(max) values of 13.2+/-2.8 mM and 13.1+/-3.1 nmol/mg protein/5 min, respectively. Concomitant administration of organic cations (1 mM) such as cimetidine, quinidine and trimethoprim inhibited both the transcellular transport and accumulation of [14C]creatinine. Furthermore, apical excretion of [14C]creatinine was not dependent on acidification of the apical medium. CONCLUSIONS: Creatinine was subjected to directional transport across renal epithelial cells from the basolateral to apical side. The organic cation transporter should be involved in the basolateral uptake of creatinine.