Could an intrarenal Cori cycle participate in the urinary concentrating mechanism?

Letter to the EditorCould an intrarenal Cori cycle participate in urinary concentrating mechanism?Lise BankirLise BankirCentre de Recherche des Cordeliers, Institut National la Santé et Médicale, Sorbonne Université, Université Paris, FranceCentre Scientifique, ERL 8228, Laboratoire Physiologie Rénale Tubulopathies, FrancePublished Online:30 Aug 2021https://doi.org/10.1152/ajprenal.00253.2021MoreSectionsPDF (185 KB)Download PDFDownload PDFPlus ToolsExport citationAdd favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmail In their recent study, Agarwal and colleagues showed how two forms of lactate dehydrogenase are distributed within renal cortex they affected by hypoxia (1). accompanying Editorial, David Sheikh-Hamad emphasized importance this “kidney shuttle” (2). Here, we want highlight another interesting feature handling that occurs medulla.In inner medulla (IM), oxygen supply is relatively poor glucose major energy source. The cleavage one into lactates produces ATP molecules. Concentration IM four- sixfold higher than cortex. Countercurrent exchange between ascending (venous) descending (arterial) vasa recta minimizes dissipation concentration gradient. It has been proposed breakdown not only provides but also contributes solute accumulation releasing osmotically active molecules (lactates) out (glucose) (3, 4). These extra solutes should help drive water from collecting ducts.Gluconeogenesis known occur kidney proximal tubule. most intense pars recta, a nephron segment expresses Na+-glucose cotransporter isoform 1 (SGLT1) its apical membrane brush border (5). Lactate shown be preferred substrate for gluconeogenesis (6). generally assumed newly formed released peripheral blood. Could renal-borne serve some function itself? Because SGLT1 can transport both directions (7), it fully conceivable could secreted lumen thus flow through downstream segments.The efferent arterioles juxtamedullary glomeruli traverse outer stripe (OS) without supplying capillaries zone. OS, blood depends almost exclusively on numerous (AVR), which surround them closely. AVR share large area contact (Fig. 2 Ref. 8). As explained above, carries issued IM. easy assume used gluconeogenesis.Taken together, these observations led us propose may (8). traditional takes place liver (which glucose) muscles consume produce lactate). kidney, glucose, produced cells, via (7). Glucose then carried with tubular fluid IM, where will metabolic when cleaved lactates. Some taken up cells again (6).The mechanism allowing mammals concentrated urine understood. This contribute process converting energy, spent gluconeogenesis, osmotic form osmoles. Moreover, present loops Henle bring fuel thick limbs OM, if luminal membrane. Such lactate-glucose-lactate cycling allows conversion chemical upper (two ATPs plus osmoles) delivered deep IM.Lactate recycling reported take isolated perfused rat (9). Assuming explanation rare cases nephrogenic glycosuria and/or fail metabolize glucose. Further studies about fate required prove or disprove putative cycle.DISCLOSURESNo conflicts interest, financial otherwise, declared authors.AUTHOR CONTRIBUTIONSL.B. conceived designed research; L.B. drafted manuscript; edited revised approved final version manuscript.REFERENCES1. Osis G, Traylor AM, Black LM, Spangler D, George JF, Zarjou A, Verlander JW, A. Expression A B isoforms mouse kidney. Am J Physiol Renal 320: F706–F718, 2021. doi:10.1152/ajprenal.00628.2020. Link | ISI Google Scholar2. D. Hints shuttle lactomone. F1028–F1029, doi:10.1152/ajprenal.00160.2021. Scholar3. Hervy S, Thomas SR. Inner medullary production urine-concentrating mechanism: flat model. 284: F65–F81, 2003. doi:10.1152/ajprenal.00045.2002. Scholar4. Zhang W, Edwards model microcirculation. 290: F87–F102, 2006. doi:10.1152/ajprenal.00168.2005. Scholar5. Ghezzi C, Loo DDF, Wright EM. Physiology SGLT1, SGLT2 GLUT2. Diabetologia 61: 2087–2097, 2018. doi:10.1007/s00125-018-4656-5. Crossref PubMed Scholar6. Conjard Martin M, Guitton J, Baverel Ferrier B. Gluconeogenesis glutamine human tubule: longitudinal heterogeneity lack response adrenaline. Biochem 360: 371–377, 2001. doi:10.1042/bj3600371. Scholar7. Eskandari EM, DD. Kinetics reverse mode Na+/glucose cotransporter. Membr Biol 204: 23–32, 2005. doi:10.1007/s00232-005-0743-x. Scholar8. Bankir L, Yang New insights urea mechanism. Kidney Int 81: 1179–1198, 2012 [Erratum 95: 469, 2019].doi:10.1038/ki.2012.67.Crossref Scholar9. Bartlett Espinal Janssens P, Ross BD. influence metabolism. 219: 73–78, 1984. doi:10.1042/bj2190073. ScholarAUTHOR NOTESCorrespondence: L. (lise.[email protected]fr). Previous Back Top Next FiguresReferencesRelatedInformationRelated articlesHints lactomone 02 Jun 2021American Journal Physiology-Renal PhysiologyReply Bankir: ever-expanding role 30 does exist kidney? PhysiologyCited ByReply kidneyGunars Anupam Agarwal30 August 2021 American Physiology, Vol. 321, No. 3 More issue > Volume 321Issue 3September 2021Pages F352-F353 Crossmark Copyright & PermissionsCopyright © Physiological Society.https://doi.org/10.1152/ajprenal.00253.2021PubMed34460352History Received July Accepted 4 Published online print September PDF download Metrics Downloaded 515 times