Characterization of intramuscular collagen in mammalian left ventricle.

Left ventricular collagen of various mammals (cat, cow, dog, pig, and rat) was successively extracted with neutral salt, and dilute acid solutions, and limited pepsin digestion. The distribution of the various types of collagen molecules in pepsin-solubilized ventricular collagen was analyzed electrophoretically on SDS-polyacrylamide gels in the presence of 3.6 M urea. Yields of dilute-acid-soluble collagen were only 0.4 to 0.6% of the total ventricular collagen, and less than 0.1% with neutral salt solution. Approx. 55-90% of the total collagen was extracted by limited pepsin digestion. Disc patterns of pepsin-soluble collagen revealed the presence of dimeric and trimeric components, as well as higher-molecular-weight aggregates in all samples of nonreduced and reduced ventricular collagen. Taken together, these findings suggest the presence of an extensive interchain and intermolecular cross-linking network in left ventricular collagen. Comparison of electrophoretical disc gel patterns of reduced and nonreduced pepsin-solubilized collagen indicated that left ventricular collagen is heterogenous in nature, consisting of a mixture of type I and type III collagen. It was evident that primarily type I components occur in ventricular collagen. The components of type III collagen molecules occurred in all investigated left ventricles in varying and consistently appreciably lower amounts. The proportions of type III and type I collagen vary in left ventricular tissue of different species.