Maintenance cultures of Kupffer cells isolated from rats of various ages: ultrastructure, enzyme cytochemistry, and endocytosis.

Sinusoidal liver cells were isolated from the livers of 3-, 12-, 30-, and 36-month-old female BN/BiRij rats by enzymatic digestion. The Kupffer cells in the sinusoidal cel suspensions were purified by centrifugal elutriation and kept in maintenance culture for periods of up to about 3 weeks. The viability and yield of Kupffer cells per gram of body weight did not change with the age of the donor rat. The ultrastructural, cytochemical, and functional characteristics of Kupffer cells as observed in perfusion-fixed liver were retained during several days of maintenance culture. The consistent observation of worm-like structures in cultured Kupffer cells indicated the reformation of the specific fuzzy coat of the cells during culture. Endogenous peroxidatic and acid phosphatase activities were evident in cultured Kupffer cells and showed the same localization as observed in perfusion-fixed liver. Kupffer cells in culture were able to endocytose colloidal carbon, latex particles (0.8 micron), horseradish peroxidase, and endotoxin, indicating the reappearance of different types of specific membrane receptors. The ultrastructural appearance of Kupffer cells was not markedly influenced by the age of the donor rat. However, with increasing age, the lysosomes showed increasing amounts of electron dense lipid-like material and iron in the form of ferritin. No qualitative age-related changes in the enzymes tested or in the endocytic capacity of the Kupffer cells were observed. On the basis of these observations, maintenance cultures of purified Kupffer cells can be considered as a valuable model for studying Kupffer cell functions, also in relation to aging phenomena.