HEPATIC REMOVAL OF I-125 DLT GELATIN AFTER BURN INJURY - A MODEL OF SOLUBLE COLLAGENOUS DEBRIS THAT INTERACTS WITH PLASMA FIBRONECTIN

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 I-125-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 I-125-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 I-125-DLT-gelatin was primarily but not exclusively hepatic Kupffer cells; I-125-DLT-asialofetuin and I-125-DLT-ovalbumin were removed by hepatocytes and sinusoidal endothelial cells, respectively. Thus, gelatin conjugated with I-125-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.