Effects of lysosomotropic agents on the hepatic uptake and storage of degraded carrageenan: Disparity in response of hepatocytes and Kupffer cells

Abstract

Rats were given 5 g/kg of a degraded carrageenan (C16) daily by stomach tube over a period of 12 weeks. Storage of C16 was seen in membrane-bound vacuoles both in hepatocytes and in mononuclear phagocytes (Kupffer cells). The stored material was metachromatic; acid phosphatase activity was detected at similar sites in hepatocytes but not in Kupffer cells. Injected horseradish peroxidase was excluded from storage vacuoles containing C16. Chloroquine caused marked changes in lysosomes (autophagic vacuoles and myeloid bodies) in hepatocytes of rats exposed to C16, but there was no evidence of fusion between these lysosomes and vacuoles containing C16. Chloroquine had no effect on Kupffer cells containing stored C16. Lysosomes containing iron-dextran, however, readily fused with the C16 vacuoles in both hepatocytes and Kupffer cells. The implications of the findings are discussed in terms of fusion between phagosomes and lysosomes.