Renal ammonia dynamics and baseline plasma levels of key ammoniagenic substrates in healthy New Zealand White rabbits

Abstract

Abstract Because the kidney of the rabbit differs in so many ways to the kidney of other eutherian mammals, it was decided to quantify to what extent renal ammoniagenesis contributes to the maintenance of normal acid – base balance in healthy rabbits. Furthermore, by analysing the plasma concentrations of known renal ammoniagenic substrates, and comparing these values to those found in humans, it was hoped to identify if there were any possible species difference in regard to a preference for a specific substrate. Blood was collected from eleven, fasted and untreated male New Zealand White rabbits. A plasma ammonia concentration of 77.2 ± 44.7 µmol / Litre (N = 11) was recorded, which is outside the normal human reference limit of 11 – 60 µmol / Litre for this analyte. 70% of the filtered plasma load of ammonia was reabsorbed by the rabbit kidneys, while 30% was excreted in the urine. No intrarenal ammoniagenesis was detected. The assayed plasma levels of the renal ammoniagenic substrates, L-glutamine, L-glutamic acid, triglycerides, non – esterified fatty acids, and D-(—)-3-Hydroxybutyrate were all found to be within normal human limits. In conclusion, the healthy rabbit, who is described zoologically as a folivore, does not generate renal ammonia to maintain its normal systemic and urinary acid – base balance. Furthermore, the plasma level of key renal ammoniagenic substrates in the rabbit were found to be no different to that which have been observed in humans.