Rhythms in morphology and function of hepatocytes.

In standard textbooks of histology, hepatocyte structure is described as being, for the most part, static. However, more than 50 years ago, it was reported that the glycogen content of rabbit hepatocytes varies significantly over 24 h. Since then, numerous investigators have confirmed this phenomenon in a variety of animals by use of morphological, histochemical and biochemical techniques, and it has been shown that the variation in glycogen content of hepatocytes corresponds with variations in enzymes related to glycogen metabolism. Moreover, there are also variations in most subcellular organelles and in many other proteins over 24 h. It is clear that circadian rhythms need to be taken into account in studies of morphology and function of hepatocytes.