Structural changes in rat liver glycogen during refeeding after fasting.

Abstract

Rats starved for 48 hr were refed on a high carbohydrate diet and killed at various intervals (3-24hr) in order to examine structural changes in liver glycogen. Glycogen was isolated by the HgCl2 method and thereafter treated with dithizone-chloroform to eliminate HgCl2. The extracted glycogen revealed typical α-particles besides β-particles but the KOH-extracted glycogen showed only β-particles. The tissue glycogen level began to increase after refeeding and reached a maximum at 18 hr. However, the iodine adsorption capacity of the HgCl2-extracted glycogen (but not the KOH-extracted one) increased by 30% in 6 hr-refed rats compared with control rats fed ad libitum, and then decreased to the control level. In the HgCl2-extracted samples, changes in glycogen S20, w after refeeding were coincident with the changes in the iodine adsorption capacity and β-amylolysis limit. Onthe other hand, these structural changes were not observed in the KOH-extracted samples. These findings supported that the HgCl2 method is useful for isolating native glycogen and suggested that the liver glycogen structure can be temporarily altered so as to have a high molecular-weight together with high iodine affinity and long outer chains.