Abstract
In fetal and in neonatal rat liver the following enzymes of glycogen metabolism and
of the upper part of the Embden-Meyerhof pathway and the pentose-phosphate-shunt were
determined: G6Pase, F1,6DPase, G6PDH, 6PGDH, HK, F6PK, PGM, PGI, Phosphorylase, glycogen
synthetase with and without G6P, and finally the lysosomal α-glucosidase.
G6Pase and FDPase showed parallel developmental changes: a tenfold increase before
birth and in total a hundredfold increase between the 16th fetal and the 5-7th neonatal
day. The activity of G6PDH and 6PGDH fell moderately from the 15th fetal day to the
20th neonatal day. Changes in F6PK could not be ascertained.
The increase of PGM and PGI before birth is twofold; there is a further increase of
25% at term. Phosphorylase was measured in the direction of glycogen breakdown and
glycogen synthesis. There is an increase in activity from the 15th fetal day to the
third day after birth; the highest raise was fivefold. After birth all values decrease
until the 20th day of life. Total glycogen synthetase showed a threefold increase
with the highest values at birth and a moderate decrease after birth. Independent
glycogen synthetase showed an increase towards term and a further increase towards
the 21st day of life. The lysosomal α-glucosidase showed a rapid twofold increase
from the last fetal days to the neonatal days.
The results, obtained from changes in enzyme activity, demonstrate a high capacity
of phosphorylation glucose in the fetal period. The ratio of G6PDH to F6PK indicates
that before birth the pentose phosphate shunt is the preferred way of oxidating glucose.
Because of the absence of FDPase and G6Pase activities before birth, the output of
glucose and the formation of F6P, gluconeogenesis is not acting. Through the rapid
increase of G6Pase and FDPase, gluconeogenesis starts immediately after birth.
Key words
Carbohydrate Metabolism - Enzymes - Rat Liver - Ontogenesis - Induction
1 With a grant of the "Deutsche Forschungsgemeinschaft"
