Prem C, Salvenmoser W, Würtz J, Pelster B
Institut für Zoologie und Limnologie, Universität Innsbruck, A-6020 Innsbruck, Austria.
Am J Physiol Regul Integr Comp Physiol. 2000 Dec;279(6):R2336-43. doi: 10.1152/ajpregu.2000.279.6.R2336.
Electron microscopical examination of gas gland cells of the physostome European eel (Anguilla anguilla) and of the physoclist perch (Perca fluviatilis) revealed the presence of significant numbers of lamellar bodies, which are known to be involved in surfactant secretion. In the perch, in which the gas gland is a compact structure and gas gland cells are connected to the swim bladder lumen via small canals, lamellar bodies were also found in flattened cells forming the swim bladder epithelium. Flat epithelial cells are absent in the eel swim bladder, in which the whole epithelium consists of cuboidal gas gland cells. In both species, Western blot analysis using specific antibodies to human surfactant protein A (SP-A) showed a cross-reaction with swim bladder tissue homogenate proteins of approximately 65 kDa and in the eel occasionally of approximately 120 kDa, probably representing SP-A-like proteins in a dimeric and a tetrameric state. An additional band was observed at approximately 45 kDa. Western blots using antibodies to rat SP-D again resulted in a single band at approximately 45 kDa in both species, suggesting that there might be a cross-reaction of the antibody to human SP-A with an SP-D-like protein of the swim bladder tissue. To localize the surfactant protein, eel gas gland cells were cultured on permeable supports. Under these conditions, the gas gland cells regain their characteristic polarity. Electron microscopy confirmed the presence of lamellar bodies in cultured cells, and occasionally, exocytotic events were observed. Immunohistochemical staining using an antibody to human SP-A demonstrated the presence of surfactant protein only in luminal membranes and in adjacent lateral membranes. Only occasionally, evidence was found for the presence of surfactant protein in lamellar bodies.
对欧洲咽鳔类鳗鱼（欧洲鳗鲡）和闭鳔鲈（河鲈）的气腺细胞进行电子显微镜检查发现，存在大量板层小体，已知这些小体参与表面活性剂的分泌。在鲈鱼中，气腺是一个紧密的结构，气腺细胞通过小管与鳔腔相连，在形成鳔上皮的扁平细胞中也发现了板层小体。鳗鱼的鳔中没有扁平上皮细胞，其整个上皮由立方形的气腺细胞组成。在这两个物种中，使用针对人表面活性剂蛋白A（SP-A）的特异性抗体进行的蛋白质免疫印迹分析显示，与鳔组织匀浆蛋白有交叉反应，分子量约为65 kDa，在鳗鱼中偶尔还会出现约120 kDa的交叉反应，可能代表处于二聚体和四聚体状态的SP-A样蛋白。在约45 kDa处观察到一条额外的条带。使用针对大鼠SP-D的抗体进行蛋白质免疫印迹分析，在这两个物种中再次在约45 kDa处出现一条单带，这表明该抗体与人SP-A可能与鳔组织中的一种SP-D样蛋白发生了交叉反应。为了定位表面活性剂蛋白，将鳗鱼气腺细胞培养在可渗透的支持物上。在这些条件下，气腺细胞恢复了其特征性的极性。电子显微镜证实培养细胞中存在板层小体，偶尔还观察到胞吐事件。使用针对人SP-A的抗体进行免疫组织化学染色表明，表面活性剂蛋白仅存在于腔面膜和相邻的侧膜中。仅偶尔在板层小体中发现表面活性剂蛋白存在的证据。
