Studies on the liver of Xenopus laevis. I. The ultrastructure of the parenchymal cell.

The liver of Xenopus laevis was examined with electron microscopy. Its structure was found to be markedly different from that of mammals, particularly regarding the morphology of the hepatocytes to be classified as typical. It was established that the main function of such a cell is the storage of glycogen, and further that it possesses only scant organelles and other inclusions. Since this type of cell was found most frequently in the liver of untreated animals, it was designated as normal cell. The fact appears noteworthy that in the normal liver of Xenopus laevis an abundance of cell types occur which are otherwise found to be proliferated under experimental conditions, e.g. cells with pronouncedly augmented RER, enlarged Golgi complexes, increased lipid inclusions etc. This high number of divergent hepatocytes and the fact that all intermediate stages between the individual extremes are present and not to be accounted for by the position of the cell within the liver was interpreted as being the expression of a cyclic passage of the various stages of activity. It is of special interest that augmented degradation of glycogen in the liver cell takes place only during vitellogenesis. Acute and chronic hunger, as well as adaptation to cold, hardly affect the morphology of the normal cell, especially as far as the glycogen is concerned. The possible causes for this are discussed.