Effect of metabolic acidosis on hindquarter glutamine and alanine release.

The relationship between hindquarter glutamine release and renal glutamine extraction was studied in rats undergoing chronic metabolic acidosis. Metabolic acidosis was induced by maintaining rats on NH4CL for four days; controls were pair-fed NH4HCO3. Metabolic acidosis increased renal glutamine extraction 8-fold and decreased arterial plasma glutamine concentration 40%. Hindquarter glutamine release rose 5-fold in acidosis due to an increased arteriovenous glutamine concentration difference and a significant rise in blood flow through the hindquarters. Both ammonia and glutamate extraction in the hindquarter increased in acidosis and could account for 25% of the glutamine nitrogen released. Alanine release by hindquarters, which exceeded glutamine release in the control animals, was greatly depressed in metabolic acidosis. The reduction in alanine nitrogen release during acidosis could account for 25% of the glutamine nitrogen released. Consequently, metabolic acidosis stimulates hindquarter glutamine release at the expense of alanine and is also supported by greater extraction of ammonia and glutamate. However, other N sources must supply nearly 50% of the glutamine nitrogen released based on balance studies.