Rat liver pit cells following administration of the glycopeptide preparation (Polyerga).

BACKGROUND/AIMS: Pit cells are specific liver population which has been shown to express NK activity against tumor and viral target cells. We investigated the influence of the glycopeptide preparation (Polyerga) as one of the biological response modifiers on liver pit cells of male Wistar rats.

MATERIALS AND METHODS

The number of pit cells was counted by light and electron microscopy in perfusion-fixed liver sinusoids. An electron microscopical cytochemical staining for endogenous peroxidase was done.

RESULTS

After a single intramuscular injection of Polyerga, a 3-to 6-fold increase in the number of pit cells was observed within a period of 1 to 7 days. Wide contact without specific junctions between pit cells and Kupffer cells was frequently detected. Granules, rod-cored vesicles and their closely related structures empty vesicles as well as hypertrophied Golgi apparatus were accumulated in the cytoplasm of pit cells next to contact surface. The number of ribosomes and polysomes in pit cell cytoplasm was significantly increased, which suggests activated protein synthesis.

CONCLUSIONS

These changes are considered to represent the morphological expression of pit cell activation. It is concluded that the glycopeptide preparation Polyerga can induce proliferation of activated pit cells in the rat liver.