In vitro inactivation of surface active properties of pulmonary surfactant by hydrogen peroxide and reversal by catalase. † 1566

Hyperoxia can generate reactive oxygen species, which are implicated in inactivation of pulmonary surfactant(PS). It is theoretically plausible to overcome this detrimental effect by administration of antioxidant. We hypothesized that by addition of H₂O₂ surface active properties of PS would be compromised but could be recovered by further addition of antioxidant such as catalase (CAT, Sigma chemical, St. Louis). In order to clarify this we prepared combinations of mixtures with Surfacten (S-TA, Tokyo Tanabe, Japan), H₂O₂ and CAT. We used Pulsating Bubble Surfactometer (Electronetics, NY) to measure in vitro minimum and maximum surface tensions(ST) and area-surface tension relationship. Results are 1) S-TA and H₂O₂ were mixed to the final concentrations of S-TA 0.625 and 1.25 mg phospholipids/ml and 0.1 and 1 mM H₂O₂, and incubated at 37°C for one hour. The minimum ST after 5 min of pulsation increased significantly and area-surface tension was lost for S-TA 0.625 mgPL/ml + 1 mM H₂O₂ mixture, but returned to control levels with recovery of hysteresis curve for S-TA 0.625 mgPL/ml. 2) When CAT 10 IU was added to S-TA 0.625 mgPL/ml + 1 mM H₂O₂ mixture, the resultant minimum ST after 5 min of pulsation dropped to the control levels.Table Figure

Table 1

In conclusion, PS could be inactivated by addition of high concentrations of H₂O₂ but surface active properties can be recovered either by increasing PS concentration or by further addition of antioxidant CAT. Therefore, we suggest that in case of suspected surfactant inactivation an increase in surfactant concentration or administration of antioxidant must be considered.