Differential activity and lack of synergy of lung surfactant proteins SP-B and SP-C in interactions with phospholipids.
This study shows that the hydrophobic lung surfactant proteins (SP)-B and SP-C are not synergistic in enhancing functionally relevant surface behaviors in films and dispersions with phospholipids, and that SP-B is more effective than SP-C in facilitating surface activity. Purified bovine SP-B, SP. C, or SP-B/C (1/1 by wt) were combined with chroma tographically purified calf lung surfactant phospholipids (PPL), or with dipalmitoyl phosphatidylcholine (DPPC) or complex phospholipid mixtures containing 75% or 50% DPPC (75% SPL or 50% SPL). Adsorption was consistently better in corresponding mixtures of phospholipids plus SP-B versus SP-C, but was not improved further by substitution of SP-B/C for SP-B. Interfacial films of DPPC or SPL plus 1.3% SP-B or 1.3% SP-C had improved respreading compared to phospholipids alone (Wilhelmy balance, 23 degrees C and 37 degrees C), but substitution of mixed SP-B/C for either pure apoprotein did not increase respreading further. Surface-excess films of phospholipids plus SP-B had higher maximum surface pressures, or maintained a high maximum pressure through more consecutive compressions, than corresponding films with SP-C. Dispersions of phospholipids plus 1.3% SP-B or mixed (1/1) SP-B/C (2.6%) rapidly lowered surface tension to < 1 mN/m in oscillating bubble studies (20 cpm, 37 degrees C), while corresponding dispersions containing SP-C reduced surface tension more slowly or reached higher minima. Mixtures of 50% SPL with SP-B versus SP-C were also better able to resist inhibition by serum albumin in bubble and adsorption studies, and inhibition resistance was not significantly improved in mixtures containing 2.6% SP-B/C (1/1) versus 1.3% SP-B. The lack of synergy in hydrophobic apoprotein function, coupled with the greater effectiveness of SP-B in improving phospholipid adsorption, dynamic surface activity, and inhibition resistance, suggests that mixtures of phospholipids plus SP-B or related peptides may be particularly relevant its clinical exogenous surfactants.
Wang
Z
Z
Department of Pediatrics, University of Rochester, NY 14642, USA.
Gurel
O
O
Baatz
J E
JE
Notter
R H
RH
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism*; D000327:Adsorption; D000818:Animals; D002417:Cattle; D009991:Oscillometry; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D011312:Pressure; D011510:Proteolipids / Q000737:chemistry / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000737:chemistry / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors
D010743:Phospholipids; D011510:Proteolipids; D011663:Pulmonary Surfactants; D015060:1,2-Dipalmitoylphosphatidylcholine; D012710:Serum Albumin, Bovine