Perinatal development of gluconeogenesis in guinea-pig liver

1. 1. At mid-gestation the activities of guinea-pig liver pyruvate carboxylase, glucose-6-phosphatase and cytosolic phosphoenolpyruvate carboxykinase were less than 0.4 unit/g, whereas the activity of fructose-1,6-diphosphatase was 1.6 unit/g. Throughout gestation the activity of cytosolic phosphoenolpyruvate carboxykinase remained unchanged while all other enzymes exhibited a 2- to 3-fold increase over the levels at mid-gestation, beginning at 45–50 days. The activities of pyruvate carboxylase and phosphoenolpyruvate carboxykinase in the foetus were largely mitochondrial. 2. 2. No increases in enzyme activities were evident in the first 2–3 hr following birth. Subsequently, increases were noted for all enzymes examined, with an overshoot occurring between 7 and 14 days post partum for pyruvate carboxylase, glucose-6-phosphatase, and fructose-1,6-diphosphatase. 3. 3. The increases in enzyme activities following birth could be prevented by treating the newborns with actinomycin D. 4. 4. In the immediate postnatal period, the degree of hypoglycaemia was not pronounced, the initial 40% drop in blood glucose level 1 hr after birth being reduced to less than 20% at 2hr. 5. 5. Livers taken from near-term foetuses and perfused immediately after Caesarean delivery synthesized appreciable amounts of glucose from lactate and glycerol. 6. 6. The data show that the capacity for hepatic gluconeogenesis in guinea-pigs is acquired before birth.