2020-04-242020-04-242015Cano Rodríguez, M.M., Calonge Castrillo, M.L. y Ilundáin Larrañeta, M.A.A. (2015). Na+-dependent and Na+-independent betaine transport across the apical membrane of rat renal epithelium. Biochimica et Biophysica Acta - Biomembranes, 1848 (10), 2172-2179.0005-27361879-2642https://hdl.handle.net/11441/95722The 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.application/pdf8 p.engAttribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/BetaineBrush-border membrane vesiclesKidneyTransportinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccesshttps://doi.org/10.1016/j.bbamem.2015.05.020