Kinetics of plasma fibronectin: increased lung tissue incorporation after postoperative bacteremia

Fibronectin is an adhesive glycoprotein that may influence the permeability of the vascular barrier. We compared the plasma disappearance of purified human fibronectin (hFn) and its incorporation into lung tissue in control nonbacteremic and bacteremic sheep after surgery to determine the influence of postoperative bacteremia on the plasma clearance and lung deposition of hFn. Lymph fistulas were surgically prepared 48 h before either saline or bacterial challenge to allow for collection of timed samples of plasma, lung lymph, and peripheral lymph. On the day of the study, the sheep were anesthetized and given either 5 X 10(8) Pseudomonas aeruginosa in saline or saline alone. In parallel, they were infused intravenously with 100 mg of hFn, and the hFn concentration in plasma, lymph, and tissue extracts was subsequently determined by enzyme-linked immunosorbent assay over an 8-h experimental interval. Localization of endogenous sheep fibronectin (sFn) and the injected hFn in serial lung tissue samples was determined by dual-label immunofluorescence. In nonbacteremic control sheep, plasma hFn levels declined with an initial rapid slope (t1/2 = 0.53 +/- 0.19 min), followed by a second, gradual slope (t1/2 = 21.7 +/- 2.5 h), whereas the concentration of hFn in lung lymph and peripheral lymph rose exponentially with time. In bacteremic sheep, the early plasma disappearance of hFn was similar, but the second phase of plasma clearance was faster (t1/2 = 7.4 +/- 0.3 h). Lung tissue from control and bacteremic sheep contained the same level of extractable hFn. However, tissue extraction followed by immunofluorescence microscopy indicated that lung tissue from bacteremic sheep contained more nonextractable hFn than lung tissue from nonbacteremic sheep. Thus postoperative bacteremia that elicits acute lung vascular injury will increase the plasma disappearance of hFn and its incorporation into the lung tissue.