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Ammonium metabolism: emphasis on energy considerations
1St. Michael's Hospital Annex, Lab No. 1, Toronto, Ont., Canada.
Mineral and Electrolyte Metabolism
|January 1, 1990
Summary
The kidney replenishes bicarbonate lost from a typical North American diet by producing ammonia (NH4+) in proximal tubule cells. This process is regulated by cellular energy demands and fuel availability.
Area of Science:
- Nephrology
- Renal Physiology
- Acid-Base Balance
Background:
- Metabolism of a typical North American diet generates a net acid load.
- The body compensates for acid load by forming CO2 and bicarbonate deficit.
- Kidneys play a crucial role in restoring bicarbonate levels.
Purpose of the Study:
- To elucidate the kidney's mechanism for generating 'new' bicarbonate.
- To identify the primary metabolic pathway involved in bicarbonate synthesis.
- To understand the regulatory factors controlling this renal bicarbonate production.
Main Methods:
- Focuses on the physiological and metabolic pathways within renal proximal convoluted tubule cells.
- Investigates the glutaminase/glutamate dehydrogenase pathway's role in ammonia and bicarbonate production.
- Examines the influence of energy turnover, renal work (sodium reabsorption), and fuel competition on this pathway.
Main Results:
- The kidney synthesizes ammonia (NH4+) and bicarbonate, excreting NH4+ in urine.
- The glutaminase/glutamate dehydrogenase pathway is the primary route stimulated by chronic metabolic acidosis.
- Renal bicarbonate production is limited by energy availability and competition for metabolic fuels.
Conclusions:
- The kidney actively generates bicarbonate to counteract dietary acid loads.
- Ammonia production via the glutaminase/glutamate dehydrogenase pathway is key to this process.
- Cellular energy status and fuel competition significantly regulate renal bicarbonate synthesis.