Effect of acute plasma fibronectin depletion on tissue fibronectin levels: analysis by a new fluorescent immunoassay.
Plasma fibronectin modulates reticuloendothelial (RE) phagocytosis of cellular and tissue debris, fibrin microaggregates, and gelatin-coated particulates. An antigenically related, but more insoluble form of fibronectin is found in various tissues and suspected to play a role in vascular permeability, cell adhesion, and wound healing. The current study developed a fluorescent immunoassay which could be utilized for the quantification of tissue fibronectin following its extraction from tissues. Additionally, the changes in tissue fibronectin induced by the intravenous injection of gelatin-coated colloids in rats (300-350 g), which acutely depletes the plasma fibronectin level, were also investigated. Injection of gelatinized RE test lipid emulsion (50 mg/100 g) depleted the plasma fibronectin at 2 hr (80-85% depletion) followed by rebound restoration within 24 hr as quantified by either electroimmunoassay or fluorescent immunoassay. RES system clearance of the test particles from the blood resulted in an acute elevation in fibronectin extractable from the liver with a normalization by 48 hr. In contrast, assay of tissue fibronectin following a single extraction revealed a decrease in lung extractable fibronectin within 2 hr following RE blockade which persisted for 24-48 hr. Extractable fibronectin in spleen and renal tissue was unaltered by RE blockade. This microfluorescent immunoassay may provide a sensitive method to quantify fibronectin in small aliquots of tissue. Increased hepatic fibronectin most likely reflects interiorization of plasma fibronectin during Kupffer cell clearance of the test particles. Decreased lung extractable fibronectin may alter lung vascular sensitivity to a subsequent septic and/or intravascular coagulation stress. Thus, similar to the labile nature of plasma fibronectin, the concentration of fibronectin in various tissues, can undergo dynamic alterations.
D000818:Animals; D001808:Blood Vessels / Q000378:metabolism; D005353:Fibronectins / Q000172:deficiency* / Q000378:metabolism; D007122:Immunoelectrophoresis; D007158:Immunologic Techniques; D008099:Liver / Q000378:metabolism*; D008168:Lung / Q000378:metabolism*; D008297:Male; D012157:Mononuclear Phagocyte System / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013050:Spectrometry, Fluorescence; D013154:Spleen / Q000378:metabolism*
D005353:Fibronectins