The purpose of this study was to explore the interrelations among energy turnover, the selection of fuels, and the production of
ammonium (NH4+) in the kidney during chronic
metabolic acidosis. Experiments were carried out in dogs because of the extensive background literature in this species. The specific question addressed was, will a diminished rate of oxidation of
fatty acids in the kidney permit the rate of extraction of
glutamine and the production of NH4+ to rise? Chronic
metabolic acidosis was induced by the ingestion of NH4Cl for 5 days to stimulate the rate of production of NH4+.
Insulin was administered to diminish the delivery of
fatty acids to the kidney. The concentration of
fatty acids in plasma fell from 350 +/- 104 to 188 +/- 45 microM, yet there was no significant increase in the rates of production of NH4+, consumption of
oxygen, or extraction of
glutamine after
insulin. Notwithstanding, there was a significant rise in the rate of extraction of
lactate by the kidney when expressed per 100-mL glomerular filtration rate. Because there was a significant decline in the level of
glutamine in plasma (512 +/- 76 to 359 +/- 42 microM) 1 h after giving
insulin, a second series of experiments was carried out. When
glutamine was infused after the
insulin period, there was no longer a fall in the concentration of this metabolite. Notwithstanding, the rates of extraction of
glutamine and production of NH4+ were not higher in the presence of
insulin. These data suggest that the rate of oxidation of
fatty acids did not limit the rate of oxidation of
glutamine in the kidneys of fed dogs with chronic
metabolic acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)