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NBCe1-A Regulates Proximal Tubule Ammonia Metabolism under Basal Conditions and in Response to Metabolic Acidosis.

Hyun-Wook LeeGunars OsisAutumn N HarrisLijuan FangMichael F RomeroMary E HandlogtenJill W VerlanderI David Weiner
Published in: Journal of the American Society of Nephrology : JASN (2018)
Renal ammonia metabolism is the primary mechanism through which the kidneys maintain acid-base homeostasis, but the molecular mechanisms regulating renal ammonia generation are unclear. In these studies, we evaluated the role of the proximal tubule basolateral plasma membrane electrogenic sodium bicarbonate cotransporter 1 variant A (NBCe1-A) in this process. Deletion of the NBCe1-A gene caused severe spontaneous metabolic acidosis in mice. Despite this metabolic acidosis, which normally causes a dramatic increase in ammonia excretion, absolute urinary ammonia concentration was unaltered. Additionally, NBCe1-A deletion almost completely blocked the ability to increase ammonia excretion after exogenous acid loading. Under basal conditions and during acid loading, urine pH was more acidic in mice with NBCe1-A deletion than in wild-type controls, indicating that the abnormal ammonia excretion was not caused by a primary failure of urine acidification. Instead, NBCe1-A deletion altered the expression levels of multiple enzymes involved in proximal tubule ammonia generation, including phosphate-dependent glutaminase, phosphoenolpyruvate carboxykinase, and glutamine synthetase, under basal conditions and after exogenous acid loading. Deletion of NBCe1-A did not impair expression of key proteins involved in collecting duct ammonia secretion. These studies demonstrate that the integral membrane protein NBCe1-A has a critical role in basal and acidosis-stimulated ammonia metabolism through the regulation of proximal tubule ammonia-metabolizing enzymes.
Keyphrases
  • anaerobic digestion
  • room temperature
  • poor prognosis
  • wild type
  • type diabetes
  • gene expression
  • dna methylation
  • ionic liquid
  • transcription factor
  • copy number