Nitrogen metabolism in goldfish, Carassius auratus (L.). Pathway of aerobic and anaerobic glutamate oxidation in goldfish liver and muscle mitochondria

Abstract

1. 1. Intact mitochondria isolated from lateral red muscle and liver of goldfish were under aerobic and anaerobic conditions incubated with glutamate, ADP and phosphate. In order to evaluate the route of glutamate oxidation, the accumulation of alanine, ammonia and aspartate was measured. 2. 2. In liver mitochondria, glutamate is exclusively oxidized via glutamate dehydrogenase, resulting in the accumulation of ammonia as the only nitrogenous end-product. This process proves to be completely blocked by anoxia. 3. 3. In red muscle mitochondria glutamate is oxidized via glutamate-oxaloacetate transaminase, resulting in the accumulation of aspartate. This process is not fully blocked by anoxia. 4. 4. These results indicate that in goldfish liver aerobic ammonia production takes place via glutamate dehydrogenase, while in muscle both aerobically and anaerobically to be produced via the purine nucleotide cycle.