Circadian variations of ultramorphology and glycogen content in hepatocytes of light-manipulated rats.

1. The biochemically and histochemically determined glycogen rhythm was found to be shifted according to the shift of the 12: 12 h light-dark cycle. Deprivation of this synchronizer does not abolish the glycogen rhythm. 2. The circadian variations of the glycogen content are accompanied by a complete reorganization of the appearance of the hepatocyte inventory of cell organelles as seen in the analysis of the electron microscopical structure of liver cells. 3. The grade of the cytologically visible circadian changes is strongly correlated with the absolute glycogen content.