COMPARATIVE EFFECTS OF SOME SERUM COMPONENTS AND PROTEOLYTIC PRODUCTSOF FIBRINOGEN ON SURFACE TENSION-LOWERING ABILITIES OF BERACTANT AND A SYNTHETIC PEPTIDE-CONTAINING SURFACTANT KL(4)(1)

The serum components of C-reactive protein, lysophosphatidylcholine, f ibrinogen, and fibrinogen proteolytic products have been shown to redu ce surface tension-lowering abilities of lung surfactant. The inhibito ry effects of these serum components were compared among four differen t surfactants: natural lung surfactant, a phospholipid mixture that ha d no surfactant proteins, KL(4) surfactant which has a synthetic surfa ctant protein B (SP-B)-like peptide, and beractant (BER) which has bot h SP-B and SP-C. The pulsating bubble surfactometer was used to measur e the surface tension of these surfactants after the addition of inhib itors. Inhibition of BER and KL(4) surfactant was observed with some s erum components within 1 min of pulsation, but was reversed after 3 mi n of pulsation for KL(4) surfactant and to a lesser extent with BER. T he surface tension of phospholipid mixture alone was significantly inc reased and did not improve with further pulsations, Natural lung surfa ctant was least inhibited and was affected only at very high fibrinoge n concentrations (5 mg/mL), At identical concentrations of these inhib itors, KL(4) surfactant was inhibited less compared with BER. We concl ude that the response of a lung surfactant to inhibitory agents may de pend on the presence or absence of surfactant-related protein(s) in th e surfactant and the concentration of exogenous surfactant used. KL(4) surfactant, which has a synthetic peptide in lieu of SP-B, resists in hibition to these serum components more than BER at similar phospholip id concentrations.