title: Ammonia transport in the kidney by Rhesus glycoproteins.
abstract: Renal ammonia metabolism is a fundamental element of acid-base homeostasis, comprising a major component of both basal and physiologically altered renal net acid excretion. Over the past several years, a fundamental change in our understanding of the mechanisms of renal epithelial cell ammonia transport has occurred, replacing the previous model which was based upon diffusion equilibrium for NH3 and trapping of NH4(+) with a new model in which specific and regulated transport of both NH3 and NH4(+) across renal epithelial cell membranes via specific membrane proteins is required for normal ammonia metabolism. A major advance has been the recognition that members of a recently recognized transporter family, the Rhesus glycoprotein family, mediate critical roles in renal and extrarenal ammonia transport. The erythroid-specific Rhesus glycoprotein, Rh A Glycoprotein (Rhag), was the first Rhesus glycoprotein recognized as an ammonia-specific transporter. Subsequently, the nonerythroid Rh glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), were cloned and identified as ammonia transporters. They are expressed in specific cell populations and membrane domains in distal renal epithelial cells, where they facilitate ammonia secretion. In this review, we discuss the distribution of Rhbg and Rhcg in the kidney, the regulation of their expression and activity in physiological disturbances, the effects of genetic deletion on renal ammonia metabolism, and the molecular mechanisms of Rh glycoprotein-mediated ammonia transport.
authors.affiliation: Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville Florida; and Division of Nephrology, Hypertension, and Transplantation, University of Florida College of Medicine, Gainesville, Florida David.Weiner@Medicine.ufl.edu.
authors.forename: I David
authors.initials: ID
authors.lastname: Weiner
authors.affiliation: Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville Florida; and.
authors.forename: Jill W
authors.initials: JW
authors.lastname: Verlander
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology; D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D027682:Cation Transport Proteins / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051379:Mice; D023421:Models, Animal
chemical_list: D027682:Cation Transport Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; C422995:RHBG protein, human; C413213:RHCG protein, human; C486033:RhBG protein, mouse; C485880:Rhcg protein, mouse; D000641:Ammonia
keywords: acid-base; ammonia; collecting duct; intercalated cell; principal cell