ABSTRACT
Figure 9-1 Inhibition of the adsorption of endogenous lung surfactant by hemoglobin. Hemoglobin (Hb) inhibits the adsorption of lavaged bovine lung surfactant (LS) when the two are added simultaneously to a stirred subphase (0.15 M NaCl + 1.4 mM CaCl2) at 37˚C. The surface pressure-time adsorption isotherms depend on the concentration of Hb and LS in analogy with the results for albumin in Table 9-1. Corresponding surface tensions are found by subtracting surface pressures from 70 mN/m. (A) 1: LS, 0.065 mg/ml; 2: LS, 0.065 mg/ml + Hb, 0.31 mg/ml; 3: LS, 0.065 mg/ml + Hb, 0.63 mg/ml; 4: Hb, 0.31-2.5 mg/ml. (B) 1: LS, 0.13 mg/ml; 2: LS, 0.13 mg/ml + Hb, 0.63-2.5 mg/ml. (C) 1: LS, 0.28 mg/ml; 2: LS, 0.28 mg/ml + Hb, 2.5-3.75 mg/ml. (Data from Ref. 453.)
In addition to inhibiting adsorption, plasma and blood proteins can compromise the dynamic surface activity of lung surfactant (Table 9-2). At a low surfactant concentration of 0.4 mg phospholipid/ml (0.5 mM), albumin and hemoglobin raise the minimum surface tension of lavaged bovine surfactant from <1 mN/m to more than 20 mN/m on the pulsating bubble surfactometer. These inhibitory effects on dynamic surface tension lowering again exhibit a strong dependence on lung surfactant concentration. When the concentration of surfactant phospholipid is raised to 0.75 mg/ml (1 mM), the detrimental effects of albumin and hemoglobin in elevating minimum surface tension during dynamic cycling are reduced even if blood protein concentration is increased (Table 9-2).
