Development of gluconeogenic enzymes in the liver of fasting or suckling newborn pigs.
Gluconeogenic enzymes and substrates were measured in the livers of fasted and suckled newborn pigs in the first 48 h postpartum. The activities at birth of glucose-6-phosphatase, fructose-1,6-diphosphatase, pyruvate carboxylase and phosphoenolpyruvate carboxykinase were, respectively, 70%, 45%, 117% and 35% of adult values. At birth, cytosolic phosphoenolpyruvate carboxykinase represented 35% of total activity, a similar distribution to that in the adult. In suckled piglets, all activities were greater at 24 and 48 h that at birth. In starved piglets, the increases were greater in all cases; the increase in cytosolic phosphoenolpyruvate carboxykinase was much more pronounced than for that for the particulate enzyme, with the former representing more than 50% of total at 48 h. The levels of gluconeogenic enzymes in the piglets in the early neonatal period would appear to be adequate for their needs and do not provide an explanation for their fasting hypoglycaemia. Hepatic levels of lactate, pyruvate, phosphoenolpyruvate, ketone bodies, and amino acids were determined in these piglets. No significant differences were observed in these metabolites between fasted and suckled animals except that glutamine was doubled in fed piglets, Evidence for the metabolic block in the livers of fasted animals was lacking and ketone bodies did not accumulate. These observations suggest that the limitations to gluconeogenesis result from unavailability of energy substrates and/or carbon precursors to the liver or the deficiency in their uptake.
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D005215:Fasting; D005635:Fructosediphosphates / Q000378:metabolism; D005943:Gluconeogenesis; D005958:Glucosephosphates / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005973:Glutamine / Q000032:analysis; D008099:Liver / Q000201:enzymology*; D010728:Phosphoenolpyruvate / Q000032:analysis; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000378:metabolism; D011766:Pyruvate Carboxylase / Q000378:metabolism; D013552:Swine
D005635:Fructosediphosphates; D005958:Glucosephosphates; D005973:Glutamine; D010728:Phosphoenolpyruvate; D005969:Glutamate Dehydrogenase; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D011766:Pyruvate Carboxylase