Distribution of Glutamine Metabolizing Enzymes and Production of Urinary Ammonia in the Mammalian Kidney

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Abstract
The distribution of the glutamine metabolizing enzymes was studied in the kidney of four mammalian species (dog, rat, rabbit and guinea pig). Glutaminase I activity of whole kidney was highest in the dog (19.1 µm NH3/gm/min.), intermediate in the rat (8.1 µm NH3/gm/min.), and low in the guinea pig (1.1 µm NH3/ gm/min.) and rabbit (0.6 µm NH3/gm/min.). In all four species, enzyme activity was highest in the cortex and inner medulla. Glutaminase II and glutamine synthetase activity were lower than glutaminase I activity in all four species. Both glutaminase II and glutamine synthetase activity were found only in the cortex and outer medulla. The relationship of the glutamine metabolizing enzymes to the production of urinary ammonia is discussed.