Renal and hepatic nitrogen metabolism during NH4Cl ingestion in protein-deprived rats.
Three groups of rats were given either a standard protein diet, a protein-free diet, or a protein-free diet with the inclusion of 0.28 M NH4Cl in their drinking water, for 10 days. Body, liver and kidney masses were decreased similarly in the protein-free and protein-free NH4Cl groups. Ingestion of protein-free diet resulted in profound systemic acidosis in both groups, the simultaneous consumption of NH4Cl having no further effect. The activities of the urea-cycle enzymes carbamoyl-phosphate synthease, ornithine transcarbamoylase, arginosuccinate lyase and arginase were significantly reduced in the protein-free group, and the simultaneous ingestion of NH4Cl had no further effect. These results indicate that ammonium ingestion does not prevent the decrease in urea cycle enzyme activities during a period of dietary-protein deprivation. Renal phosphate-dependent glutaminase activity was unchanged in the protein-free group, but was significantly higher with simultaneous NH4Cl consumption, suggesting that the renal adaptation to acid ingestion is not compromised by a lack of dietary protein. Urinary ammonia excretion also increased in rats consuming protein-free diet and NH4Cl. Urinary urea excretion was greater in rats receiving protein-free diet and NH4Cl than in rats receiving protein-free diet only, at all time-points examined. These data demonstrate that urea synthesis is driven primarily by the need to dispose of protein-derived ammonia rather than bicarbonate.
Lardner
A L
AL
Physiology Department, University College Galway, Ireland.
O'Donovan
D J
DJ
D000138:Acidosis / Q000378:metabolism; D000643:Ammonium Chloride / Q000008:administration & dosage*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001769:Blood / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage; D005260:Female; D005972:Glutaminase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014508:Urea / Q000097:blood / Q000378:metabolism / Q000652:urine
D001639:Bicarbonates; D004044:Dietary Proteins; D000643:Ammonium Chloride; D014508:Urea; D005972:Glutaminase; D009584:Nitrogen