The effect of glucagon on ureagenesis from ammonia by isolated rat hepatocytes

Glucagon, at a maximally effective concentration of 1 μM, stimulated by 35% the rate at which rat hepatocytes synthesized urea from 10 mM NH₄Cl in the presence of 10 mM ornithine. The rate at which citrulline accumulated in the incubations was relatively unchanged by the presence of glucagon.Mitochondria isolated from glucagon treated hepatocytes were observed to synthesize citrulline from 10 mM NH₄Cl and 10 mM ornithine more rapidly than did mitochondria isolated from untreated hepatocytes.The role of the intracellular malate concentration in the regulation of the rate of urea synthesis, and the changes observed in the cellular content of malate in response to glucagon are discussed.