Renal regulation of interorgan glutamine flow in metabolic acidosis

The regulation of interorgan glutamine flow was studied in control and chronically metabolically acidotic rats. Net glutamine extraction or production across the kidneys, gut, liver, and hindquarters was determined in fasted anesthetized animals from organ blood flows and the arteriovenous glutamine concentration difference. In control animals glutamine flows from the hindquarters to the splanchnic bed. In chronic acidosis glutamine production by the hindquarters rose threefold and was redirected to the kidneys; splanchnic bed glutamine uptake was eliminated. Associated with this was a 39% fall and a 62% rise in arterial glutamine and ammonia concentrations, respectively. Removing the kidneys from the circulation returned arterial glutamine and ammonia concentrations to control nonacidotic levels within 30 min. Net glutamine production by the hindquarters decreased, whereas splanchnic bed glutamine extraction increased. Hindquarter glutamine production appears to be modulated by renal venous ammonia; splanchnic bed glutamine extraction is load dependent, reflecting the influence of renal glutamine consumption on the steady-state arterial levels. Thus the removal of the kidneys returns interorgan glutamine flow to that observed in nonacidotic animals consistent with a major role of the kidneys in regulating glutamine flow and nitrogen metabolism in chronic metabolic acidosis.