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Regulation of glutamine transport during acidosis in renal proximal tubule cell
Author(s) -
Lin Chengmao,
Karinch Anne,
Wolff Brynn,
Tunke Laura,
Meng Qinghe,
Pan Ming,
Souba Wiley
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a351
Subject(s) - acidosis , glutamine , transporter , metabolic acidosis , medicine , chemistry , epithelial polarity , endocrinology , biology , biochemistry , cell , amino acid , gene
Objective We identified the Na+‐dependent amino acid transporter System N (SN1) as the carrier responsible for the striking increase in renal basolateral glutamine transport during acidosis in vivo. The importance of SN1 in regulating renal ammoniagenesis in acidosis was investigated in vitro using a renal epithelial cell line (LLC‐PK 1 ) with characteristics of proximal tubule cells. Methods LLC‐PK 1 cells were grown in transwell plates and exposed to control (pH 7.4) or acidosis (pH 6.9) medium for 48 hours. SN1‐mediated glutamine transport across the basolateral membrane was measured in confluent cells. SN1 mRNA was measured by real‐time PCR. SN1 protein was measured by Western analysis. Ammonia concentration in the apical and basal compartments was measured using an enzyme‐linked assay. Results The activity of SN1‐mediated glutamine transport across the basolateral membrane was significantly higher in acidosis (control: 138 ± 36 nmol/mg/min vs. 252 ± 52 nmol/mg/min, acidosis, p≤ 0.01). SN1 mRNA and protein levels were elevated approximately 2‐fold in acidosis. Treatment with acidic media also increased ammonia secretion across the apical membrane (control: 28.4 ± 5.1 μg/ml vs. 37.5 ± 6.9 μg/ml, acidosis, p ≤ 0.001) and decreased secretion across the basolateral membrane (control: 21.3 ± 3.1 μg/ml vs. 14.0 ± 2.0 μg/ml, acidosis, p ≤ 0.01). Conclusion Via uptake of glutamine, SN1 transporter may play a major role in the regulation of renal ammoniagenesis. The LLC‐PK 1 cell grown in transwell plates is a valuable model as it allows us to study the mechanism of acidosis‐induced ammoniagenesis in vitro.