Location and identification of the collagen found in the 14.5-d rat embryo visceral yolk sac.

Abstract

The collagens associated with 14.5-d [day] rat visceral yolk sacs were localized and identified by a variety of procedures. Morphological examination showed that both the visceral epithelium and mesothelium rested upon thin basement membranes; the majority of the extracellular matrix consisted of a stroma containing occasional cells and abundant banded fibrils. Immunohistochemistry at the EM level showed that the basement membranes specifically cross-reacted with antibodies directed against mouse basement membrane components; the stroma specifically cross-reacted with antibodies directed against rat type I collagen. Extractions of acellular visceral yolk sacs and subsequent analyses showed that type I collagen components were prevalent. In vitro biosynthetic studies showed only the presence of type I procollagen components (or their conversion products) and .alpha.-fetoprotein. These findings, taken together with our previous studies on the 14.5-d rat parietal yolk sac, provide protein markers for studying the origin of cells in rat parietovisceral yolk sac carcinomas.