1. Model of proximal ammonia transport.
Model of proximal ammonia transport. Glutamine serves as the primary metabolic substrate for ammoniagenesis. Proximal tubule glutamine uptake involves transport across the apical membrane, primarily via BoAT-1, and across the basolateral membrane by SNAT3. Complete metabolism of each glutamine results in generation of two NH4+ and two bicarbonate ions. Bicarbonate is transported across the basolateral membrane via NBCe-1A. Ammonium secretion across the apical membrane occurs primarily via NHE3-mediated Na+/NH4+ exchange, with a lesser contribution by parallel H+ and NH3 transport. BoAT-1, apical Na+-dependent neutral amino acid transporter-1; NBCe-1A, electrogenic sodium-bicarbonate cotransporter, isoform 1A; NHE3, sodium/hydrogen exchanger 3; SNAT3, sodium-coupled neutral amino acid transporter-3.
I. David Weiner et al. CJASN 2015;10:
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