Ammonia Transporters and Their Role in Acid-Base Balance.
Acid-base homeostasis is critical to maintenance of normal health. Renal ammonia excretion is the quantitatively predominant component of renal net acid excretion, both under basal conditions and in response to acid-base disturbances. Although titratable acid excretion also contributes to renal net acid excretion, the quantitative contribution of titratable acid excretion is less than that of ammonia under basal conditions and is only a minor component of the adaptive response to acid-base disturbances. In contrast to other urinary solutes, ammonia is produced in the kidney and then is selectively transported either into the urine or the renal vein. The proportion of ammonia that the kidney produces that is excreted in the urine varies dramatically in response to physiological stimuli, and only urinary ammonia excretion contributes to acid-base homeostasis. As a result, selective and regulated renal ammonia transport by renal epithelial cells is central to acid-base homeostasis. Both molecular forms of ammonia, NH3and NH4+, are transported by specific proteins, and regulation of these transport processes determines the eventual fate of the ammonia produced. In this review, we discuss these issues, and then discuss in detail the specific proteins involved in renal epithelial cell ammonia transport.
Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; and Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida.
I David
0000-0002-0046-0600
ID
Weiner
Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; and Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida.
Jill W
0000-0002-4096-4897
JW
Verlander
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*
D026901:Membrane Transport Proteins; D000641:Ammonia