Physicochemical and ultrastructural studies on glycogenosomes in newborn rat hepatocytes

In the newborn rat liver, glycogenosomes appeared at about 6 hours after birth and gradually increased in number, despite high activity of lysosomal acid alpha-glucosidase. The glycogenosomes then disappeared completely with 2 days after birth. Glycogen extracted from fetal rat liver differed in molecular structure from that of adult rat liver. In measurements of optical rotatory dispersion (ORD) and circular dichroism (CD) absorption spectra, fetal-type glycogen showed the Cotton effect whereas the adult rat liver glycogen did not. The degree of branching and S-values of the two glycogens were also different. With the disappearance of glycogenosomes, fetal-type glycogen disappeared completely, and adult-type glycogen then appeared strongly. This was demonstrated in the intracytoplasmic matrix by electron microscopy. The present experiments indicate that glycogenosomes may be formed even under conditions of high acid alpha-glucosidase, and that autophagy of glycogen macromolecules in the lysosomal system is closely related to different structural features of fetal-type glycogen in the neonatal period.