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目的肺泡Ⅱ型上皮细胞对维持肺表面活性物质的动态平衡和肺免疫功能具有极其重要的意义。地塞米松对急性肺损伤肺泡Ⅱ型上皮细胞超微结构的影响目前仍不清楚。该研究探讨急性肺损伤时及应用地塞米松干预后肺泡Ⅱ型上皮细胞超微结构的动态变化。方法72只21dSD幼鼠随机分为对照组、急性肺损伤组和地塞米松治疗组。肺损伤组的幼鼠腹腔注射脂多糖(LPS)(4mg/kg)以建立急性肺损伤模型。对照组注射等量生理盐水。地塞米松治疗组在注射LPS1h后腹腔注射地塞米松(5mg/kg)。每组随机选取8只幼鼠分别于注射LPS或生理盐水后24、48、72h处死。取左肺下1mm3的肺组织固定于2.5%戊二醛中待透射电镜检查。结果注射LPS24h后,肺损伤组大鼠AT Ⅱ细胞微绒毛消失,板层小体数量增加。24及48h板层小体呈指环状绕核排列。48h出现巨大空泡变性样的板层小体。细胞核形态不规则,部分核边界不清。72h板层小体数目明显减少,核仁从细胞核消失,一些细胞核出现核溶解。注射LPS后24h地塞米松治疗组板层小体聚集在AT Ⅱ细胞内同侧,并于该侧发生“胞吐”现象。48h线粒体肿胀、聚集,脊断裂,板层小体数目减少。72h板层小体数目增多,并重新呈指环状绕核排列。结论LPS诱导的急性肺损伤肺泡Ⅱ型上皮细胞超微结构的一系列变化呈时间依赖性。地塞米松能减轻急性肺损伤中肺泡Ⅱ型上皮细胞损伤和促进肺泡Ⅱ型上皮细胞的功能恢复。
Objective Alveolar type II epithelial cells are of great importance for maintaining the dynamic balance of pulmonary surfactant and pulmonary immune function. The effect of dexamethasone on the ultrastructure of alveolar type Ⅱ epithelial cells in acute lung injury is still unclear. This study explored the dynamic changes of the ultrastructure of alveolar type II epithelial cells after acute lung injury and dexamethasone intervention. Methods Seventy-two SD rats were randomly divided into control group, acute lung injury group and dexamethasone treatment group. Lungs (4mg / kg) were intraperitoneally injected into the lung injury group to establish acute lung injury model. The control group was injected with normal saline. Dexamethasone treated rats were injected with dexamethasone (5mg / kg) ip on day 1 after LPS injection. Each group of eight randomly selected young rats were killed at 24,48,72 h after injection of LPS or normal saline. Take lung tissue 1mm3 left lung fixed in 2.5% glutaraldehyde to be examined by transmission electron microscopy. Results After injection of LPS for 24 hours, the microvilli of AT Ⅱ cells in the lung injury group disappeared and the number of lamellar bodies increased. 24 and 48h lamellar body was ring-shaped core around the arrangement. 48h appeared a huge vacuolar degeneration of the lamellar body. Irregular nuclear morphology, part of the nuclear boundary is unclear. 72h lamellar bodies significantly reduced the number of nucleolus disappeared from the nucleus, some nuclei appear nuclear lysis. In the dexamethasone treated group, lamellar bodies accumulated in the same side of AT Ⅱ cells 24h after injection of LPS, and “exocytosis” occurred on this side. 48h mitochondria swelling, aggregation, spinal rupture, the number of lamellar bodies reduced. 72h lamellar body number increased, and re-ring-shaped core around the nuclear arrangement. Conclusion A series of changes in the ultrastructure of alveolar type Ⅱ epithelial cells induced by LPS in a time-dependent manner are time-dependent. Dexamethasone can reduce alveolar type Ⅱ epithelial cell injury in acute lung injury and promote the functional recovery of alveolar type Ⅱ epithelial cells.