Immunoelectron microscopic observations on the localization of fibronectin in normal human lung

The localization of fibronectin was examined in normal human lung using immunoelectron microscopy. Fibronectin staining was present not only in the endothelial, alveolar epithelial and bronchial epithelial basal laminae and associated with interstitial collagen fibrils and elastic fibers, but also in basal laminae of fibroblasts and smooth muscle cells. There was a periodicity in the staining of fibronectin on collagen fibrils. Reaction products against fibronectin were present in intracellular organelle including cisternae of smooth endoplasmic reticulum of endothelial cells and those of rough endoplasmic reticulum of fibroblasts. No other cells contained reaction products. The localization of fibronectin was compared with that of ruthenium red staining in normal human lung. The localization of fibronectin was consistent with that of proteoglycan.