title: Potential role of ammoniagenesis in the hypocalciuric effect of phosphorus in rats.
abstract: OBJECTIVE
  Hypocalciuria associated with a high phosphorus intake is known to be both a parathyroid hormone and non-parathyroid hormone dependent event. The present study was designed to define the role that ammoniagenesis may play in the non-parathyroid hormone dependent pathway.
  
  
  METHODS
  Male rats, initially weighing 160 g, were fed a purified diet containing, in g/kg diet, a single level of protein (200) and variable inorganic phosphorus (1.8, 4.5, 9.0) for 20 days.
  
  
  RESULTS
  Food intake and body weight were similar for the three groups. Significant inverse correlations were found for both urinary calcium and phosphorus and for urinary ammonia nitrogen and calcium excretion (r = -0.62, p < 0.01). Urinary ammonia nitrogen excretion was highly correlated with both phosphorus intake (r = 0.89, p < 0.001) and urinary phosphorus (r = 0.88, p < 0.001). Urinary urea nitrogen tended to vary inversely with phosphorus intake. High dietary phosphorus decreased the activity of glutamine synthetase and increased the activity of glutaminase I in kidney.
  
  
  CONCLUSIONS
  Tying-up some of the hydrogen ions destined for excretion by phosphorus-stimulated ammoniagenesis could reduce the interfering effect of hydrogen ion on kidney calcium reabsorption and provide a mechanism to explain why phosphorus can have a direct positive impact upon tubular calcium reabsorption.
authors.affiliation: Department of Nutrition and Food Management, College of Home Economics and Education, Oregon State University, Corvallis, USA.
authors.forename: F L
authors.initials: FL
authors.lastname: Cerklewski
mesh_terms: D000641:Ammonia / Q000378:metabolism* / Q000652:urine; D000818:Animals; D002118:Calcium / Q000652:urine*; D004435:Eating; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D005972:Glutaminase / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000201:enzymology; D008297:Male; D009584:Nitrogen / Q000652:urine; D010758:Phosphorus / Q000008:administration & dosage / Q000494:pharmacology* / Q000652:urine; D051381:Rats; D017207:Rats, Sprague-Dawley; D014508:Urea / Q000652:urine; D015430:Weight Gain
chemical_list: D010758:Phosphorus; D000641:Ammonia; D014508:Urea; D005972:Glutaminase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen; D002118:Calcium