The decline of plasma
fibronectin after surgery,
trauma, and
burn, as well as during
severe sepsis after injury, appears to limit hepatic Kupffer cell phagocytic activity.
Intravenous infusion of
gelatin-coated particles to simulate blood-borne particulate collagenous tissue debris in the circulation after injury also depletes plasma
fibronectin. We used soluble
gelatin conjugated with 125I-labeled
dilactitol tyramine (DLT-
gelatin) as a model of soluble collagenous tissue debris. We studied its blood clearance as well as organ localization in normal and postburn rats.
Fibronectin-deficient plasma harvested early after
burn exhibited limited ability to support in vitro phagocytic uptake of the gelatinized microparticles by Kupffer cells in liver tissue from normal rats. However, Kupffer cells in liver tissue from normal and postburn rats phagocytized the test particles at a normal rate when incubated in normal plasma. The DLT-
gelatin ligand bound to
fibronectin in a dose-dependent manner as verified by its capture with anti-
fibronectin coated
plastic wells when coincubated with purified
fibronectin. By gel filtration chromatography, the binding of
fibronectin with the DLT-
gelatin ligand was readily detected, resulting in the formation of a high-molecular-weight complex. In normal animals the plasma clearance and liver localization of 125I-DLT-gelatin was competitively inhibited by infusion of excess nonradioactive
gelatin. The blood clearance and liver localization of the soluble
gelatin ligand were also impaired after
burn injury during periods of
fibronectin deficiency similarly to the pattern observed with
gelatin-coated microparticles. By autoradiography, the cellular site for the uptake of the 125I-DLT-gelatin was primarily but not exclusively hepatic Kupffer cells; 125I-DLT-asialofetuin and 125I-DLT-ovalbumin were removed by hepatocytes and sinusoidal endothelial cells, respectively. Thus,
gelatin conjugated with
125I-DLT can be used to simulate blood-borne soluble collagenous tissue debris after
burn. It rapidly binds to plasma
fibronectin before its hepatic Kupffer cell removal, and its blood clearance is markedly delayed after
burn injury during periods of plasma
fibronectin deficiency.