Leakage of Protein into Lungs of Preterm Ventilated Rabbits Is Correlated with Activation of Clotting, Complement, and Polymorphonuclear Leukocytes in Plasma

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Abstract
We investigated whether leakage of protein in lungs of preterm ventilated rabbits of 28- and 29-d gestational age is correlated with activation of clotting, complement, and polymorphonuclear leukocytes (PMN) in plasma. We found signs of systemic activation of clotting, complement, and PMN in ventilated 28-d gestational age rabbits, as indicated, respectively, by increased median plasma fibrin monomer concentrations (83 versus 40% of normal adult rabbit plasma in nonventilated 28-d gestational age rabbits,p < 0.01), decreased median plasma CH50 activity (112versus 122 U/L in nonventilated 28-d gestational age rabbits,p < 0.05), and increased median plasma β-glucuronidase concentrations (159 versus 97% of maximal activated adult rabbit plasma in nonventilated 28-d gestational age rabbits, p < 0.05). We did not find signs of systemic activation in the ventilated 29-d gestational age group. Higher median total protein concentrations in alveolar wash of the ventilated 28-d gestational age rabbits (2.7 versus 1.3 mg/mL in the nonventilated rabbits, p < 0.01) indicated protein leakage into the lungs, and this protein leakage was more pronounced in the lungs of ventilated 28-d gestational age rabbits than in those of ventilated 29-d gestational age rabbits (2.1 mg/mL, p < 0.01). The total protein concentration in the alveolar wash of all 28-d gestational age rabbits was correlated with the concentration of fibrin monomers (ρ = 0.51,p = 0.035) and β-glucuronidase (ρ = 0.61, p = 0.011), and the CH50 activity (ρ = -0.73, p = 0.002) in plasma. We conclude that leakage of protein in lungs of preterm ventilated rabbits of 28-d gestational age is correlated with activation of clotting, complement, and PMN in plasma. This activation process may contribute to lung injury by intravascular and intraalveolar deposition of fibrin and formation of proteinaceous edema.