Content-dependent activity of lung surfactant protein B in mixtures with lipids.
The content-dependent activity of surfactant protein (SP)-B was studied in mixtures with dipalmitoyl phosphatidylcholine (DPPC), synthetic lipids (SL), and purified phospholipids (PPL) from calf lung surfactant extract (CLSE). At fixed SP-B content, adsorption and dynamic surface tension lowering were ordered as PPL/SP-B approximately SL/SP-B > DPPC/SP-B. All mixtures were similar in having increased surface activity as SP-B content was incrementally raised from 0.05 to 0.75% by weight. SP-B had small but measurable effects on interfacial properties even at very low levels < or =0.1% by weight. PPL/SP-B (0.75%) had the highest adsorption and dynamic surface activity, approaching the behavior of CLSE. All mixtures containing 0.75% SP-B reached minimum surface tensions <1 mN/m in pulsating bubble studies at low phospholipid concentration (1 mg/ml). Mixtures of PPL or SL with SP-B (0.5%) also had minimum surface tensions <1 mN/m at 1 mg/ml, whereas DPPC/SP-B (0.5%) reached <1 mN/m at 2.5 mg/ml. Physiological activity also was strongly dependent on SP-B content. The ability of instilled SL/SP-B mixtures to improve surfactant-deficient pressure-volume mechanics in excised lavaged rat lungs increased as SP-B content was raised from 0.1 to 0.75% by weight. This study emphasizes the crucial functional activity of SP-B in lung surfactants. Significant differences in SP-B content between exogenous surfactants used to treat respiratory disease could be associated with substantial activity variations.
Wang
Z
Z
Department of Pediatrics, University of Rochester, Rochester, NY 14642, USA.
Baatz
J E
JE
Holm
B A
BA
Notter
R H
RH
D000818:Animals; D007700:Kinetics; D008055:Lipids / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D037701:Pulmonary Surfactant-Associated Protein B / Q000737:chemistry / Q000378:metabolism*
D008055:Lipids; D010743:Phospholipids; D037701:Pulmonary Surfactant-Associated Protein B