Chromatin supraorganization and extensibility in mouse hepatocytes following starvation and refeeding

Abstract

Background: The effect of 48 h of starvation and of 48 h of refeeding subsequent to starvation on chromatin supraorganization and extensibility was studied in hepatocytes from adult mice.

Methods: Methods used involved topochemical assays, image analysis, gravity action, and polarization microscopy.

Results: Starvation increased the chromatin packing states, especially in areas of noncondensed chromatin, and induced drastic decreases in concanavalin A reactivity due to nuclear matrix glycoproteins and the frequency of nuclei with chromatin extensibility under gravity. Changes in chromatin packing state were accompanied by shifts of nuclear areas of part of the nuclear population to smaller values but did not affect the respective Feulgen-DNA amounts except for a few nuclei. The extent of chromatin unpackaging, but not of frequency of nuclei with formation of extended chromatin fibers, in starved mice that were refed was greater than in well-fed controls. Refeeding induced increase in Feulgen-DNA amounts and regain and redistribution of concanavalin A-reactive nuclear glycoproteins. However, the duration of refeeding used was probably insufficient to reestablish the stereo arrangement of the chromatin-nuclear matrix and to restore chromatin fluidity to the level seen in well-fed mice.

Conclusions: The changes in the liver cell nuclei associated with starvation and refeeding of adult mice involved chromatin supraorganization, hepatocyte proliferation (refeeding), and the loss, regain, and redistribution of nuclear proteins, especially nuclear matrix components, related to chromatin organization and extensibility. These changes are suggested as favoring the silencing and reactivation of transcriptional activities, depending on the organism's nutritional state.