RGD Reference Report - Na+-dependent and Na+-independent betaine transport across the apical membrane of rat renal epithelium. - Rat Genome Database

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Na+-dependent and Na+-independent betaine transport across the apical membrane of rat renal epithelium.

Authors: Cano, Mercedes  Calonge, María L  Ilundáin, Anunciación A 
Citation: Cano M, etal., Biochim Biophys Acta. 2015 Oct;1848(10 Pt A):2172-9. doi: 10.1016/j.bbamem.2015.05.020. Epub 2015 May 29.
RGD ID: 30309905
Pubmed: (View Article at PubMed) PMID:26028423
DOI: Full-text: DOI:10.1016/j.bbamem.2015.05.020

The low renal excretion of betaine indicates that the kidney efficiently reabsorbs the betaine filtered by the glomeruli but the mechanisms involved in such a process have been scarcely investigated. We have detected concentrative and non-concentrative betaine transport activity in brush-border membrane vesicles (BBMV) from rat renal cortex and medulla. The concentrative system is the Sodium/Imino-acid Transporter 1 (SIT1) because it is Na+- and Cl--dependent, electrogenic and is inhibited by an anti-SIT1 antibody. Its apparent affinity constant for betaine, Kt, is 1.1±0.5 mM and its maximal transport velocity, Vmax, 0.5±0.1 nmol betaine/mg protein/s. Inhibitors of the Na+/Cl-/betaine uptake are L-proline (75%) and cold betaine, L-carnitine and choline (40-60%). Neither creatine, TEA, taurine, β-alanine, GABA nor glycine significantly inhibited Na+/Cl-/betaine uptake. The non-concentrative betaine transport system is Na+- and H+-independent, electroneutral, with a Kt for betaine of 47±7 μM and a Vmax of 7.8±1 pmol betaine/mg protein/s. Its transport activity is nearly abolished by betaine, followed by L-carnitine (70-80%) and proline (40-50%), but a difference from the Na+/Cl-/betaine transport is that it is inhibited by TEA (approx. 50%) and unaffected by choline. The underlying carrier functions as an antiporter linking betaine entry into the BBMV with the efflux of either L-carnitine or betaine, an exchange unaffected by the anti-SIT1 antibody. As far as we know this is the first work reporting that betaine crosses the apical membrane of rat renal epithelium by SIT1 and by a Na+- and H+-independent transport system.

Annotation

Gene Ontology Annotations    

Biological Process

Molecular Function

Objects Annotated

Genes (Rattus norvegicus)
Slc6a20  (solute carrier family 6 member 20)


Additional Information