Gluconeogenesis in a carnivorous bird (black vulture).

MIGLIORINI, R. H., C. LINDER, J. L. MOURA, AND J. A. S. VEIGA. Gluconeogenesis in a carnivorous bird (black vulture). Am. J. Physiol. 225(6) : 1389-l 392. 1973.-Gluconeogenesis studies were carried out in the black vulture (Coragyps atratus), a carnivorous bird. The blood sugar levels of the black vulture were markedly resistant to 3 days of fasting. Also, no increase in plasma FFA levels was detected during this period. While 50% of initial glycogen content was still present after a 3-day fast, muscle glycogen was reduced 6Oa/,. The rate of glucose synthesis in liver slices from fed black vultures was more than twice that in slices from chickens, granivorous birds of similar body size. The activities of three “key” enzymes of the gluconeogenetic pathway: glucose-6-phosphatase, fructose1 ,6-diphosphatase, and PEP carboxykinase, were also higher in black vulture livers than in chicken livers. PEP carboxykinase activity attained extremely high values in the carnivorous bird and was almost equally divided between the cytosol and mitochondrial fraction; about 70-80% of the activity in whole-liver homogenate was recovered in these two compartments. The high capacity for glucose synthesis of the carnivorous bird is probably related to the highprotein content of the food. drolase, EC 3.1.3.1 l), and phosphoenolpyruvate carboxykinase (guanosine triphosphate : oxaloacetate carboxylyase (transphosphorylating, EC 4.1.1.32) were measured in the liver of the black vulture and compared to those of the domestic chicken, a granivorous bird of similar body size.