目的：细胞周期素D1（CyclinD1）、p21CIP1是主要的肺细胞增殖调控蛋白，参与肺发育、肺损伤修复过程。本研究观察大鼠肺发育过程中小管期、囊泡期、肺泡期等不同阶段CyclinD1和p21CIP1的表达特征。方法：分别于孕20 d、21 d、生后0 d、3 d、7 d、14 d、21 d取胎鼠或新生鼠肺组织标本（n=6），用免疫组织化学技术检测CyclinD1和p21CIP1在大鼠肺发育各期定位表达，免疫印迹半定量检测大鼠肺发育过程中CyclinD1和p21CIP1蛋白的表达。结果：在大鼠肺发育各期中，小管期CyclinD1蛋白表达最强，肺泡期CyclinD1蛋白表达最弱。而p21CIP1蛋白表达在小管期最弱，肺泡期最强。 在小管期CyclinD1阳性表达主要定位于上皮细胞，p21CIP1表达阴性。囊泡期CyclinD1表达强度明显减弱，CyclinD1 和p21CIP1阳性表达主要定位于上皮细胞和间质细胞。肺泡期p21CIP1表达最强，CyclinD1阳性表达主要定位于间质细胞，p21CIP1阳性表达主要定位于上皮细胞。结论：大鼠肺发育过程中CyclinD1和p21CIP1在各期表达部位及数量有差异，在小管期, CyclinD1表达最强，细胞增殖活动明显较囊泡期和肺泡期旺盛,肺泡期p21CIP1表达最强与肺泡分隔及成熟有关。

OBJECTIVE: CyclinD1 and p21CIP1 are major proteins to regulate lung cell proliferation and involved in lung development and lung injury reparation. This study aimed to explore the expression manners of CyclinD1 and p21CIP1 at canalicular, saccular and alveolar stages during lung development in Sprague-Dawley rats. METHODS: Lung tissues were obtained from fetal rats of 20 and 21 days gestational ages, and neonatal rats at 0, 3, 7, 14 and 21 days (n=6). Lung tissues were used for histopathology and the protein analysis of CyclinD1 and p21CIP1 (immunohistochemistry and Western blot). RESULTS: The strongest expression of CyclinD1 and the weakest expression of p21CIP1 occurred at 20-21 days gestation (canalicular stage). At the canalicular stage, CyclinD1 was mainly expressed in epithelial cells, and the expression of p21CIP1was negative. At the saccular stage, the expression of CyclinD1 decreased significantly and the p21CIP1 expression increased significantly. Positive expression of CyclinD1 and p21CIP1 was found in epithelial cells and interstitial cells. At the alveolar stage, the CyclinD1 expression was the lowest and the p21CIP1 expression was the highest. The positive expression of CyclinD1 was found in interstitial cells and that of p21CIP1 was found in epithelial cells. CONCLUSIONS: The location and quantity of CyclinD1 and p21CIP1 expression are different at various stages during lung development in rats. A strongest CyclinD1 expression found in the canalicular stage may be associated a high lung cell proliferation. A strongest p21CIP1 expression found in the alveolar stage may be associated with alveolar maturity.