Ultrastructural localization of the major components of the extracellular matrix in normal mouse liver.

We have investigated the extracellular and intracellular distribution of the major components of the hepatic extracellular matrix: types I and IV collagen (CI and CIV), type III procollagen (PCIII), fibronectin (FN) and laminin (LM) in the normal mouse liver by electron microscopy, using the indirect immunoperoxidase method. Extracellular localization of CI and PCIII revealed the typical collagen fibrils and small bundles in portal tracts and Disse's space. Faint extracellular deposition of CIV was detectable in basement membranes of portal structures and as discontinuous precipitates in Disse's space. FN strongly reacted in Disse's space and formed a continuous layer as well as strands between hepatocytes and endothelial cells. Moderate LM reaction was seen along the sinusoids in discrete spots and in basement membranes surrounding bile ducts and blood vessels. The cellular source of these components was demonstrated to be of mixed origin. Hepatocytes synthesized very little CI and large amounts of FN. Additionally, CI was produced by periportal fibroblasts. Fat-storing cells clearly participated in the production of PCIII, CIV and LM. LM synthesis was also found in bile duct cells and the cells of Hering's canal.