Concentration dependence of a poly-leucine surfactant protein C analogue on in vitro and in vivo surfactant activity.
BACKGROUND
Modified natural surfactants currently used for treatment of respiratory distress syndrome contain about 0.5-1% (w/w phospholipids) of each of the surfactant proteins SP-B and SP-C. The supply of these preparations is limited and synthetic surfactant preparations containing lipids and peptides are under development.


OBJECTIVE
To investigate the potential of different concentrations of the SP-C analogue SP-C33 in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (68:31, w/w).


METHODS
Surface activity was evaluated in pulsating and captive bubble surfactometers and in immature newborn rabbits.


RESULTS
Preparations containing >or=1% SP-C33 achieve minimum surface tension <5 mN/m indicating good biophysical activity, and increase tidal volumes in premature rabbit fetuses to the same level as a modified natural surfactant preparation does. Alveolar patency at end expiration, as evaluated by measurement of lung gas volumes, histological assessment of alveolar expansion and determination of alveolar volume density, was lower in the animals treated with synthetic surfactant than in those receiving modified natural surfactant.


CONCLUSIONS
These data suggest that SP-C33 is similarly efficient as the native peptide in improving surface properties of phospholipids mixtures and in increasing lung compliance in surfactant-deficient states, but that other components are needed to maintain alveolar stability at low airway pressures.
Almlén
Andreas
A
Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
Stichtenoth
Guido
G
Robertson
Bengt
B
Johansson
Jan
J
Curstedt
Tore
T
D000818:Animals; D000831:Animals, Newborn; D004305:Dose-Response Relationship, Drug; D005540:Forced Expiratory Flow Rates / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D010713:Phosphatidylcholines / Q000494:pharmacology*; D010715:Phosphatidylglycerols / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000473:pathology; D037721:Pulmonary Surfactant-Associated Protein C / Q000494:pharmacology*; D011817:Rabbits; D012121:Respiration, Artificial; D013500:Surface Tension / Q000187:drug effects; D013990:Tidal Volume / Q000187:drug effects
D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D037721:Pulmonary Surfactant-Associated Protein C; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine