Effect of fasting for two days on the excretion of ammonium in dogs with chronic metabolic acidosis.
BACKGROUND
The source of glutamine for renal ammonium production is ultimately dietary protein in the fed state and body proteins in fasting.


OBJECTIVE
Our objective was to determine if less NH(+)(4) would be excreted by fasted dogs with chronic metabolic acidosis resulting in conservation of lean body mass.


METHODS
Acid-loaded fed and fasted dogs were given 10 mmol NH(4)Cl/kg for 5 days; the fasted group had food withheld on days 4 and 5.


RESULTS
The renal production of NH(+)(4) was not significantly different in both acid-loaded groups, yet the rate of NH(+)(4) excretion was significantly lower in the fasted dogs (8 vs. 21 mmol NH(+)(4)/mmol creatinine). The urine pH was significantly higher (6.0 versus 5.5) while titratable acid and the urine flow rate were significantly lower in these fasted dogs. Despite nearly equal urine flow rates and Na(+) excretion rates after an infusion of saline, the fasted dogs failed to increase the rate of excretion of NH(+)(4) to rates seen in the fed group.


CONCLUSIONS
The lower rate of excretion of NH(+)(4) in fasted, acidotic dogs appeared to be due to a lower distal H(+) secretion. This may help preserve lean body mass during fasting.
Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ont., Canada. mitchell.halperin@utoronto.ca
Mitchell L
ML
Halperin
Surinder
S
Cheema-Dhadli
Ching-Bun
CB
Chen
D000138:Acidosis / Q000652:urine*; D000818:Animals; D002908:Chronic Disease; D004285:Dogs; D005215:Fasting; D000644:Quaternary Ammonium Compounds / Q000652:urine*
D000644:Quaternary Ammonium Compounds