ALTERATIONS IN RENAL AND HEPATIC NITROGEN-METABOLISM IN RATS DURING HCL INGESTION

The effect of prolonged metabolic acidosis on hepatic and renal enzyme s associated with nitrogen metabolism was investigated, The rates of u rinary ammonia and urea excretion were also determined, Administration of 9 mmol HCl daily for 8 days resulted in severe metabolic acidosis, The activity of the first two enzymes of the urea cycle, carbamoyl ph osphate synthetase (CPS) and ornithine transcarbamoylase (OTC), was 30 % greater in chronically acidotic rats than in pair-fed controls, Ther e was also a fivefold increase in renal phosphate-dependent glutaminas e (PDG) activity and an 18 to 24-fold increase in renal ammonia excret ion, Urea excretion was not constant in the acidotic group, decreasing during the first 4 days and gradually returning to pair-fed control l evels between the fourth and eighth day, The return to control levels of urinary urea excretion coincided with the plateau of urinary ammoni a excretion that occurred by day 4 in the acidotic group, A similar pa ttern of urea nitrogen excretion has been observed in both NH4Cl and H Cl acidosis, ie, an initial decrease in urea excretion followed by a g radual increase with time, These results suggest that hepatic urea syn thesis does not play a significant role in long-term regulation of the acid-base balance in rats during chronic metabolic acidosis. Copyrigh t (C) 1998 by W.B. Saunders Company.