Matrix composition in opossum esophagus

The esophagus of mammalian species is organized into mucosa, connective tis sue, and muscle, but little is known about the matrix of these layers. We s tudied by immunohistochemistry the distribution of collagens, fibronectin, versican, and elastin in the smooth muscle segment of the American opossum. Cryosections were exposed to specific antibodies and fluorescent-stained u sing conjugates of rhodamine or isothiocyanate. Staining was scored by two observers. We found that collagen I was prominent in the submucosa and in t he muscular septa; collagen III formed fibrillar meshes in the lamina propr ia and the submucosa but was virtually absent from the epithelial and muscu lar layers; collagen IV was restricted to the: base of the epithelium; coll agen V, in contrast to collagen III, was prominent in epithelium and muscul aris mucosae and sparse in muscular septa and submucosa, Fibronectin distri bution followed collagen III; it formed layers in lamina propria and submuc osa and strands in muscle septa and between individual muscle cells. Versic an distribution followed collagen V; it was prominent in large muscle septa and formed thick sheets at the boundaries of submucosa/circular muscle and of circular/longitudinal muscle. We also determined the tissue contents of protein, hexuronic acid, and fibronectin. The mucosal layers exceeded the muscular layers in their content of hexuronic acid and fibronectin but not protein, We conclude that individual layers of the smooth muscle esophagus each have their own characteristic matrix. Lamina propria and submucosa are similar with regard to fiber orientation but lamina propria contains relat ively more collagen III (small fibril) and submucosa comparatively more col lagen I (large fibril). Nonfibrillar collagen V and versican are particular ly prominent specifically on the boundaries between contracting muscle tiss ue and connective tissue framework.