Renal ammonium metabolism is the primary component of net acid excretion and thereby is critical for acid-base homeostasis. Briefly, ammonium is produced from glutamine in the proximal tubule in a series of biochemical reactions that result in equimolar bicarbonate. Ammonium is predominantly secreted into the luminal fluid via the apical Na(+)/H(+) exchanger, NHE3. The thick ascending limb of t...

The acquisition of nutrients requires tight regulation to ensure optimal supply while preventing accumulation to toxic levels. Ammonium transporter/methylamine permease/rhesus (AMT/Mep/Rh) transporters are responsible for ammonium acquisition in bacteria, fungi, and plants. The ammonium transporter AMT1;1 from Arabidopsis thaliana uses a novel regulatory mechanism requiring the productive inter...

Introduction Previously we demonstrated in rats that chronic hyperkalemia had no effect on ammonium secretion by the proximal tubule in vivo but that high K+ concentrations inhibited ammonium absorption by the medullary thick ascending limb in vitro. These observations suggested that chronic hyperkalemia may reduce urinary ammonium excretion through effects on medullary transport events. To exa...

Rhbg is a nonerythroid membrane glycoprotein belonging to the Rh antigen family. In the kidney, Rhbg is expressed at the basolateral membrane of intercalated cells of the distal nephron and is involved in NH4+ transport. We investigated the substrate specificity of Rhbg by comparing transport of NH3/NH4+ with that of methyl amine (hydrochloride) (MA/MA+), often used to replace NH3/NH4+, in oocy...

Ammonium sulfate [(NH4)2SO4] is one of the most widely used nitrogen-based fertilizer in agriculture, and has been produced for over 150 years. However, limited research has been done to investigate the eco-toxic effects of ammonium sulfate, commonly present in surface runoff. This study therefore aimed to investigate the effects of varying ammonium sulfate concentrations on the normal physiolo...

An adjuvant composition containing a) one or more alkyl glucamides of the formula (I), wherein R1 represents a linear or branched alkyl group having 5 to 9 carbon atoms, R2 represents an alkyl group having 1 to 3 carbon atoms; b) at least one water-soluble ammonium salt, preferably selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium nitrate urea, ammonium phosphat...

Starved cells of Nitrosomonas europaea and further ammonia oxidizers were able to rapidly accumulate ammonium and hydroxylamine to an internal concentration of about 1 and 0.8 M, respectively. In kinetic studies, the uptake/accumulation rates for ammonium [3.1 mmol (g protein)(-1) min(-1)] and hydroxylamine [4.39 mmol (g protein)(-1) min(-1)] were determined. The uptake and accumulation process...

The fission yeast Schizosaccharomyces pombe undergoes a switch from yeast to filamentous invasive growth in response to certain environmental stimuli. Among them is ammonium limitation. Amt1, one of the three ammonium transporters in this yeast, is required for the ammonium limitation-induced morphological transition; however, the underlying molecular mechanism remains to be understood. Cells l...

The ammonium permease Mep2 induces a switch from unicellular yeast to filamentous growth in response to nitrogen limitation in Saccharomyces cerevisiae and Candida albicans. In S. cerevisiae, the function of Mep2 and other ammonium permeases depends on the protein kinase Npr1. Mutants lacking NPR1 cannot grow on low concentrations of ammonium and do not filament under limiting nitrogen conditio...