AMINO ACID EXTRACTION AND AMMONIA METABOLISM BY THE HUMAN KIDNEY DURING THE PROLONGED ADMINISTRATION OF AMMONIUM CHLORIDE*

Abstract

In an attempt to clarify the role of amino acids in the adaptive increases of renal ammonia production during chronic metabolic acidosis, 12 renal clearance studies with renal vein catheteriza-tion were performed in normal human subjects before and during mild NH4Cl acidosis. True renal blood flow was measured by PAH clearance and extraction, free amino acids by column chromatography, and glutamine by a specific enzymatic assay. In general, control subjects had positive A-V differences (net uptake) for glutamine, glycine, proline, taurine, valine, and isoleucine, and negative A-V differences (net release) for ammonia, serine, threonine, glutamic, alanine, cystine, leucine, tyrosine phenylalanine, histidine, ornithine, and arginine. Glutamine extraction could account for 63% of total renal ammonia release. During acidosis, urine ammonia excretion increased 2 1/2 times without a significant rise of venous ammonia release. The renal uptakes of glutamine, glutamic acid, were increased. The percentage of total ammonia release which could arise from glutamine did not differ from the control observations. No changes were observed in the other patterns of amino acid uptake or release which could definitely account for the increased ammonia synthesis which occurred during mild metabolic acidosis.