Ammonium transport and the role of the Na,K-ATPase.
Ammonium (NH4+) excretion varies appropriately with changes in acid-base balance and represents the major regulatable component of net acid excretion. The transport of ammonium can occur by 'diffusion trapping', or active H+ secretion in parallel with passive NH3 diffusion. In addition, direct NH4+ transport is important in many nephron segments. Since NH4+ and K+ have a similar hydrated radius, these ions share common transport pathways in many renal and nonrenal cell types. For example, these ions compete for a common binding site on the Na,K-ATPase. In addition to Na+ pump-mediated NH4+ transport, the Na,K-ATPase generates an electrochemical gradient across the cell membrane which affects other H+ and NH4+ transport pathways. In this review, the role of the Na+ pump on each of these renal ammonium transport mechanisms will be reviewed.
Wall
S M
SM
Division of Renal Diseases and Hypertension, University of Texas, Medical School at Houston 77030, USA.
D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D007668:Kidney / Q000378:metabolism*; D007679:Kidney Medulla / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism; D008138:Loop of Henle / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*
D000644:Quaternary Ammonium Compounds; D000641:Ammonia; D000254:Sodium-Potassium-Exchanging ATPase