Polymeric collagen isolated from the human intestinal submucosa.

The intestinal submucosal layer has a special interest in view of its commercial use in sausage casings and also due to its importance in any study of normal and pathological changes in the human intestine. Although the submucosal layer has long been known to be a collageneous structure, no detailed report has been published for the isolation of highly pure submucosal collagen together with its chemical analysis and electron-microscopic appearance. Earlier work from this laboratory has been concerned with the isolation and characterization of pure polymeric collagens from tendon and skin (Steven, 1964; Steven and Jackson, 1967), cornea (Freeman, Steven, and Jackson, 1968), intervertebral disc (Steven, Broady, and Jackson, 1968), and articular and intercostal cartilages (Steven, Broady, and Jackson, 1969). In each of these preparations it was necessary to pretreat the homogenized tissue with crude bacterial oc-amylase or ethylenediaminetetraacetate (EDTA) in order to release the collagen fibrils from the tissue matrix in which they were embedded. In the present study the polymeric collagen fibrils of the intestinal submucosa could be released by treatment with dilute acetic acid alone. The amino-acid composition of these polymeric collagen fibrils indicated that they consisted of at least 95% pure collagen. The purity of the polymeric collagen was further improved after treating the tissue beforehand with crude bacterial oc-amylase or with EDTA.