The effects of actinomycin D on newborn rat liver were studied by using biochemical assays, electron microscopy, and quantitative morphometry. Actinomycin prevented the normal postnatal rise in acid a 1,4 glucosidase (maltase) activity and the breakdown of lysosomal glycogen. The results suggest that the postnatal increase in acid glucosidase activity is protein synthesis dependent. This enzyme is critical for the catabolism of the lysosomal glycogen in newborn rat hepatocytes.
Acid a 1,4 glucosidase (maltase) is a critical enzyme for the degradation of glycogen included in lysosomes. Its inborn absence in Pompe's disease results in accumulation of the undigested polysaccharide in autophagic vacuoles (Hers, 1963). Liver acid glucosidase activity is low at birth but increases in the immediate postnatal period. Glycogen included in the lysosomes is thoroughly mobilized during this period (Kotoulas and Phillips, 1971; Kotoulas et al., 1971;Kotoulas, 1981). It is not known whether the increase in enzyme activity and the mobilization of polysaccharide are protein synthesis dependent or not. In this paper the effects of the protein synthesis inhibitor, actinomycin, on liver acid glucosidase activity and on lysosomal glycogen breakdown in newborn rats are presented.
MATERIALS AND METHODS
Animals and Handling of Tissues