Glycogenesis in the liver of the fetal guinea pig.

In the developing fetal liver of many animals, the appearance of glycogen in quantities demonstrable by classical chemical methods is a relatively tardy and abrupt event. For example, using Sahyun and Alsberg’s (1) modification of Pfliiger’s technique, Hard et al. (2) have shown in the guinea pig that there is no detectable liver glycogen up to the 56th day of gestation (term 66 days) but that it is abundant within the following week. Several observations indicate that onset of glycogenesis is due to changes in the hepatic cells themselves and not to extrinsic factors such as hormones. Glycogen appears in chick cardiac muscle prior to its appearance in the liver (3), chick hepatic cells, placed in tissue culture before differentiation of the pancreatic islets and before glycogen storage, gain with time the ability to form and store glycogen (4), and liver cells transplanted from a preglycogen stage chick embryo onto the chorioallantois of a chick, the liver of which contained glycogen, failed to elaborate glycogen earlier than its controls left in situ (5, 6). In our experimental approach we have been largely concerned with an investigation in the developing liver of the fetal guinea pig of those enzymes and cofactors known to control glycogen formation. The approach has been in major part directed to the question: Is there an absence of one or more of these essential components which may account for the absence of glycogen in the early liver? In addition, we have confirmed the findings of Hard et al. on the time of appearance of glycogen in the liver of the