Akino T
Department of Biochemistry, Sapporo Medical College, Japan.
Nihon Kyobu Shikkan Gakkai Zasshi. 1992 Dec;30 Suppl:5-14.
Pulmonary surfactant is a complex mixture of phospholipids and proteins which is synthesized and secreted by alveolar type II cells. Its presence is essential to prevent the collapse of alveoli at the end of expiration. Recently, it has been demonstrated that in addition to its reduction of surface tension of alveolar surfaces, pulmonary surfactant exhibits several other functions in the alveolar lining layer, and surfactant proteins are definitely involved in the expression of these functions. The present study first focused on the recent advances in basic research of hydrophilic surfactant apoproteins, SP-A and SP-D. Both are glycoproteins with C-type lectin structure at the C-terminal region and collagenous structure at the N-terminal half of the proteins. We revealed that SP-A binds specifically to dipalmitoylphosphatidylcholine and galactose-ceramide and asialo GM2, while SP-D binds specifically to phosphatidylinositol and glucose-ceramide. We discuss the physiologic and metabolic roles of the specific lipid binding with surfactant proteins of the surfactant system. We next studied changes in pulmonary surfactant in respiratory diseases using anti-human SP-A monoclonal antibodies. We demonstrated SP-A immunoglobulin complex in the sera of patients with idiopathic pulmonary fibrosis and pulmonary alveolar proteinosis.
肺表面活性物质是一种由磷脂和蛋白质组成的复杂混合物，由肺泡Ⅱ型细胞合成并分泌。它的存在对于防止呼气末肺泡塌陷至关重要。最近，已证明除了降低肺泡表面张力外，肺表面活性物质在肺泡内衬层还表现出其他几种功能，并且表面活性物质蛋白肯定参与了这些功能的表达。本研究首先聚焦于亲水性表面活性物质载脂蛋白SP-A和SP-D基础研究的最新进展。二者均为糖蛋白，在蛋白质的C末端区域具有C型凝集素结构，在N末端一半具有胶原结构。我们发现SP-A特异性结合二棕榈酰磷脂酰胆碱、半乳糖神经酰胺和脱唾液酸GM2，而SP-D特异性结合磷脂酰肌醇和葡萄糖神经酰胺。我们讨论了表面活性物质系统中表面活性物质蛋白特异性脂质结合的生理和代谢作用。接下来，我们使用抗人SP-A单克隆抗体研究了呼吸系统疾病中肺表面活性物质的变化。我们在特发性肺纤维化和肺泡蛋白沉积症患者的血清中证实了SP-A免疫球蛋白复合物。
