Laminin-secreting yolk sac carcinoma of the rat. Biochemical and electron immunohistochemical studies.

Basement membranes have been difficult to analyze biochemically because they represent a small fraction of most normal tissues and because they are extremely difficult to solubilize. The use of mouse tumors such as the parietal yolk sac carcinoma and the EHS sarcoma, in which basement membrane is one of the major biosynthetic products, has provided new insights into our understanding of basement membranes. One of the disadvantages of the mouse tumor system is the small size of the tumor-bearing animals. For this reason we decided to explore whether embryo-derived yolk sac carcinomas produced in rats could be suitable models to study basement membranes. Unlike its counterparts in the mouse the rat embryo-derived yolk sac carcinoma produces a multilamellar extracellular matrix that, morphologically, closely resembles basement membranes of non-neoplastic origin. The laminin isolated from the rat embryo-derived yolk sac is similar to that derived from the EHS sarcoma, and antibodies raised against this laminin of neoplastic origin react with all basement membranes of normal tissues tested. These antibodies were used to define the ultrastructural localization of laminin in normal rat kidney. We concluded that the rat embryo-derived yolk sac carcinoma is a useful experimental system to study basement membranes and their components such as laminin, type IV collagen, and heparan sulfate.