Endocytosis via the scavenger- and the mannose-receptor in rainbow trout (Salmo gairdneri) pronephros is carried out by nonphagocytic cells

Abstract

Endocytosis of modified human serum albumin (HSA) and mannose-terminated glycoproteins was studied in pronephros cells from rainbow trout (Salmo gairdneri). Blood clearance and tissue uptake of dinitrophenylated human serum albumin (DNP-HSA) was dependent on the number of DNP-groups conjugated to the albumin molecule. Uptake of DNP35-HSA in isolated pronephros cells was saturable. Pronephros cells also internalized the mannose-terminated glycoprotein invertase by a receptor-mediated process. DNP-HSA and invertase were recovered in the same cell fractions when pronephros cells containing in vivo endocytosed ligands were separated by density gradient centrifugation. The cells endocytosing these ligands were apparently not macrophages. The macrophages were recovered in cell fractions with higher densities. They were identified by their ability to adhere to glass and to carry out phagocytosis. Cultured macrophages did not endocytose chemically modified albumin (DNP-HSA and formaldehyde-treated albumin) and mannose-terminated glycoproteins (ovalbumin) in vitro. These ligands were not recovered in glass adherent pronephros cells after in vivo endocytosis of the proteins. The present data suggest that macrophages in rainbow trout pronephros possess neither the receptor for chemically modified albumin, the scavenger receptor, nor the mannose-specific receptor.

In vitrodegradation ofAeromonas salmonicidaandLimulus polyphemushemocyanin by Atlantic salmon,Salmo salarL. macrophages

“…In contrast to LPH adsorbed to microsilica, soluble LPH was only slightly degraded for the period of time tested. These results are in agreement with observations by Dannevig et al (1990;1994). These authors studied both in vivo and in vitro uptake of soluble and colloidal substances.…”

Scavenger endothelial cells of vertebrates: A nonperipheral leukocyte system for high-capacity elimination of waste macromolecules

“…Hyaluronan accumulated exclusively in salmon kidney sinusoidal endothelium (unpublished) and cod endocardium (17). Ligands for the mannose receptor accumulated in heart of cod and kidney of the salmonid and rainbow trout, and also in liver of the two fishes (24)(25)(26).…”

Characterisation of a long-term cell line (SHK-1) developed from the head kidney of Atlantic salmon (Salmo salarL.)

“…Thus, the SHK-1 cells did not seem not to possess the mannose-receptor. Binding and uptake of ligands specific for the scavenger-receptor, DNP-HSA (Dannevig et al, 1990) and fBSA (Eskild et al, 1986), were also not detected, further supporting the conclusion that the SHK-1 cells are of leucocytic origin. The receptors for asialoglycoproteins (AOM), transferrin and Ig seemed not to be expressed on these cells.…”

“…Previous studies have shown that, for example, sinusoidal endothelial cells were present in a suspension of head kidney cells enriched in macrophages (Dannevig et al, 1990). These endothelial cells had a very high endocytic capacity and possessed both a mannose-specific receptor and the scavenger receptor, while macrophages expressed these receptors to a lesser extent (Dannevig et al, 1990;Gjøen & Berg, 1992;. The ability of the SHK-1 cells to endocytose various ligands was therefore studied.…”

“…Ricin was kindly provided by Jean Pierre Frenoy, Institute Pasteur, Paris. Preparation of dinitrophenylated HSA (DNP-HSA) (Dannevig et al, 1990), formaldehyde-treated BSA (fBSA) (Eskild et al, 1986), asialoorosomucoid (AOM) (Tolleshaug, 1981) and Atlantic salmon serum Ig (Falk et al, 1991) were as previously described. Carrier free Na 125 I was obtained from Institute for Energy Technology, Kjeller, Norway.…”