Functional Characterization of Apical Transporters Expressed in Rat Proximal Tubular Cells (PTCs) in Primary Culture

Abstract

Since in vitro cell culture models often show altered apical transporter expression, they are not necessarily suitable for the analysis of renal transport processes. Therefore, we aimed here to investigate the usefulness of primary-cultured rat proximal tubular cells (PTCs) for this purpose. After isolation of renal cortical cells from rat kidneys, PTCs were enriched and the gene expression and function of apical transporters were analyzed by means of microarray, RT-PCR and uptake experiments. RT-PCR confirmed that the major apical transporters were expressed in rat PTCs. Na(+)-dependent uptake of α-methyl-d-glucopyranoside (αMG), ergothioneine and carnitine by the PTCs suggests functional expression of Sglts, Octn1 and Octn2, respectively. Inhibition of pH-dependent glycylsarcosine uptake by low concentration of cephalexin, which is a β-lactam antibiotics recognized by Pepts, indicates a predominant role of high affinity type Pept2, but not low affinity type Pept1, in the PTCs. Moreover, the permeability ratio of [(14)C]αMG (apical to basolateral/basolateral to apical) across PTCs was 4.3, suggesting that Sglt-mediated reabsorptive transport is characterized. In conclusion, our results indicate that rat PTCs in primary culture are found to be a promising in vitro model to evaluate reabsorption processes mediated at least by Sglts, Pept2, Octn1 and Octn2.

Pharmacological and pathophysiological roles of carnitine/organic cation transporters (OCTNs: SLC22A4, SLC22A5 and Slc22a21)

“…Similar characteristics of carnitine transport have been observed in brush‐border membrane vesicles isolated from kidney cortex . In kidney epithelial cells in primary culture, sodium dependence of carnitine uptake from the luminal side across the apical membrane has been reported in rats and humans . Sodium ion‐dependent electrogenic transport is consistent with reabsorptive transport at the renal tubules.…”

Potential Toxicity of Polymyxins in Human Lung Epithelial Cells

“…The notable difference in polymyxin B susceptibility between A549 and HK-2 cells may be due to the differential expression of membrane transporters such as megalin, which exists in the latter but not in lung epithelial cells (26). Very likely, uptake of polymyxins is mainly by PEPT2 in A549 cells (27) and by both PEPT2 and megalin in HK-2 cells (28,29).…”

Polydatin Protecting Kidneys against Hemorrhagic Shock‐Induced Mitochondrial Dysfunction via SIRT1 Activation and p53 Deacetylation

“…Expression of mitochondrial proapoptotic proteins such as cytoplasmic cytochrome C and Bax was increased. It has been reported that p53 is an important transcription factor involved in regulation of mitochondrial apoptosis and that it can regulate the permeability of the outer membranes of mitochondria [ 19 ]. Therefore, the protein expression, intracellular distribution, and acetylation level of p53 in the renal cortex after HS/R were measured.…”

“…The other portion of kidney tissue was used for isolation of RTECs by a method described previously, with slight modifications [ 19 , 20 ]. Briefly, the cortex was cut into fragments.…”