An Immunohistological and Immunogold Study on the Fibronectin Reacions in Rat Lung Differentiation / 대한흉부외과학회지

ABSTRACT

BACKGROUND: Fibronectins(FN) are large, dimeric glycoproteins present in the plasma, loose connective tissues, and some basal lamina in vivo and synthesized by a number of cells in vitro, including lung fibroblasts, and alveolar macrophages. FN can affect the migration, proliferation, differention, and even apoptosis of various cell types, all considered necessary for organogenesis. This study was undertaken to detect the changes of localization and activity of FN, a glycoprotein molecule, in stages of lung differentiation in rats. MATERIAL AND METHOD: The experimental animals(Sprague-Dawley strain) were divided into 8 groups, a control group(adult male rats), and experimental groups of 17th day fetus, 20th day fetus, first day newborn, second day newborn, 3rd day newborn, 5th day new born, 7th day newborn. We used the immunohistological stain method with gold particle to obtain the data for distribution of FN in the alveoli, blood vessels, terminal bronchioles, alveolar macrophages and type II pneumocytes. This study revealed the FN reactions at the light and electron microscopic levels. RESULT: At 17th day fetal stage, FN reactions in fetal lung were strong on the blood vessels and moderate on the stroma. At 20th day fetal stage, FN reactions were strong on the blood vessels. After birth, FN reactions in alveolar basement membrane were maximum in the 5th and 7th day newborns. FN reactions in the blood vessels were observed to be moderate in first and second day newborns, but decreased in third day newborns. FN reactions in alveolar macrophages increased after birth. FN reactions in terminal bronchioles gradually increased after birth. 6. In type II pneumocytes, FN reactions were observed to be moderate in 1st and 3rd day newborns. CONCLUSION: Immunohistochemical analysis of rat lungs at various developmental stages revealed increased deposition of FN during the pseudoglandular stage of lung development, coinciding with the period of branching morphogenesis. Also, FN is released from type II pneumocytes. This observation, together with the strategic location of FN, suggests a role in airway formation.