The breakdown of glycogen in the lysosomes of newborn rat hepatocytes: the effects of glucose, cyclic 3',5'-AMP and caffeine.

The effects of parenteral glucose, cyclic AMP and caffeine on the breakdown of glycogen in the lysosomes of newborn rat hepatocytes, were studied by using biochemical assays, electron microscopy and quantitative morphometry. Glucose prevented the normal postnatal increase in lysosomal volume, acid alpha 1,4 glucosidase activity and lysosomal glycogen breakdown. On the contrary, cyclic AMP and caffeine promoted this increase. There was a positive correlation between liver cyclic AMP concentration and acid glucosidase activity (R = 0.84, p < 0,001). Cyclic AMP also induced a change in the shape of lysosomes. The postulation that glucagon secreted after birth is the natural stimulus for the cyclic AMP-mediated postnatal increase in acid glucosidase activity and mobilization of the lysosomal glycogen in rat hepatocytes, is supported by these experimental findings.