Gluconeogenesis in developing rat kidney cortex

Abstract

1. Gluconeogenesis in developing rat kidney cortex was studied by assaying the activities of two enzymes, glucose 6-phosphatase and phosphoenolpyruvate carboxykinase, and by measuring glucose formation in tissue slices. 2. Glucose 6-phosphatase and phosphoenolpyruvate carboxykinase are present in late foetal (21-22-day-old) tissue and increase rapidly postnatally. Maximum activity of phosphoenolpyruvate carboxykinase occurs at 7 days of age, followed by a decline to the adult level. Glucose 6-phosphatase activity rises during the first 2 postnatal weeks and then declines. 3. Late foetuses synthesize glucose from both pyruvate and l-glutamate. The rate increases during the first 2 weeks to above adult levels. Synthesis is always higher from pyruvate than from glutamate. 4. The effect of 24hr. starvation was studied in perinatal animals. The results indicate that the ability to increase the rate of glucose synthesis as a result of starvation is not present at birth, but develops some time after the second postnatal day.

Carbohydrate metabolism in pregnancy

“…' Studies based on direct assay for relevant enzymes in liver suggest that meaningful gluconeogenesis does not occur in the rat fetus (46,47). Recent infusion studies in the intact animal have challenged this thesis (36) and limited gluconeogenesis has been demonstrated with fetal rat kidney cortex in vitro (48). The present data do not resolve the controversy.…”

Anatomical and developmental patterns of facilitative glucose transporter gene expression in the rat kidney.

“…Hence, the expression of the low affinity GT2 by the proximal tubules is consistent with a role in the movement ofglucose from tubular epithelium into peritubular vasculature. The high level of renal GT2 gene expression in the perinatal period may be related to the fact that the kidney alone seems to be responsible for gluconeogenesis during this time before expression of gluconeogenic enzymes by the liver (25). This is the first study to describe the localization of GT5 in the kidney.…”

The postnatal development of gluconeogenic enzymes in guinea‐pig kidney cortex

“…The gluconeogenic pathway is present both in liver and kidney cortex, but evidence from studies in the rat indicate that there is a temporal difference in the development of gluconeogenic capacity in the two tissues [5,12]. Glucose 6-phosphatase, fructose 1,6-diphosphatase, phosphoenolpyruvate carboxykinase (mitochondrial) and pyruvate carboxylase are all present in the liver at birth in the guinea-pig [6], and the ability to carry out gluconeogenesis from lactate and alanine has recently been demonstrated in the perfused livers of prematurely delivered guinea-pigs [13].…”

“…Newborn rats, on the other hand, are able to carry out gluconeogenesis only at very slow rates, and this is said to result from the virtual absence of phosphoenolpyruvate carboxykinase in the livers of these animals [14]. The capacity for renal gluconeogenesis in the newborn rat, on the other hand, is acquired at birth and is demonstrable in tissue taken from the pre-term foetus [5].…”

“…and phosphoenolpyruvate carboxykinase (EC 4.1.1.36.) in the newborn rat kidney have been shown to increase quite substantially in the period following birth [5]. On the other hand, no detailed study of the development of gluconeogenic enzymes in the liver of animals with a bimodal distribution of phosphoenolpyruvate carboxykinase such as the guinea-pig have been reported until recently [6].…”