Submitted on August 10, 2007
Accepted on February 13, 2008
Surfactant proteins B and C are both necessary for alveolar stability at end-expiration in premature rabbits with respiratory distress syndrome
Andreas Almlen1, Guido Stichtenoth1, Bim Linderholm1, Marie Haegerstrand-Bjorkman1, Bengt Robertson2, Jan Johansson3, and Tore Curstedt4*
1 Molecular Medicine and Surgery, Clinical Chemistry, Stockholm, Sweden
2 Molecular Medicine and Surgery, Clinical Chemistry, Stockholm, Sweden; United States
3 Anatomy, Physiology and Biochemistry, Uppsala, Sweden
4 Molecular Medicine and Surgery, Clinical Chemistry, Stockholm, Sweden; , Swaziland
* To whom correspondence should be addressed. E-mail: Tore.Curstedt{at}karolinska.se.
Modified natural surfactant preparations, used for treatment of respiratory distress syndrome (RDS) in premature infants, contain phospholipids and the hydrophobic proteins SP-B and SP-C. Herein the individual and combined effects of SP-B and SP-C were evaluated in premature rabbit foetuses treated with airway instillation of surfactant and ventilated without positive end-expiratory pressure. Artificial surfactant preparations composed of synthetic phospholipids 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG)/1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphoethanolamine, 55:25:15:5 (by weight) or DPPC/POPG, 68:31 (w/w), mixed with either 2% (w/w) of porcine SP-B, SP-C, or a synthetic poly-Leu analogue of SP-C (SP-C33) dido not stabilise the alveoli at the end of expiration, as measured by low lung gas volumes of about 5 ml/kg after 30 min of ventilation (modified natural surfactant 18 ml/kg, untreated controls 1-2 ml/kg). However, treatment with phospholipids containing both 2% SP-B and mixed with 2% SP-C/SP-C33 approximately doubled lung gas volumes.gave lung gas volumes of 11 ml/kg, while treatment with phospholipids containing 4% SP-C33 gave lung gas volumes of only 4-5 ml/kg. Doubling the SP-C33 content did not affect lung gas volumes. The tidal volumes were similar in all groups receiving surfactant. This shows that SP-B and SP-C exerts different physiological effects, sincethat both proteins are needed to establish alveolar stability at end-expiration in this animal model of RDS, and that an optimal synthetic surfactant probably requires the presence of mimics of both SP-B and SP-C.
