Collagen type distribution in the mammalian left ventricle during growth and aging.

Left ventricular collagen of rats aged 1,4,8, and 24 months, as well as young and adult pigs and beef, was successively extracted with neutral salt and dilute acid solutions and limited pepsin digestion. The distribution of type I and III collagen molecules in pepsin-solubilized collagen was analyzed with sodium dodecyl sulphate polyacrylamide gel electrophoresis in the presence of 3.6 M urea, under nonreducing and reducing conditions. Yields of dilute-acid-soluble collagen ad neutral-salt-soluble collagen were extremely low (0.3-0.8%, and less than 0.3% of total starting collagen, respectively), indicating the presence of an extensive interchain and intermolecular cross-linking network in left ventricular tissue of young and mature mammals. Comparison of protein patterns in electrophoresis gels indicated that myocardial collagen consists primarily of type I collagen molecules. The components of type III collagen also occurred in all investigated preparations, in varying and consistently lower proportions. The ratio of type III to type I collagen changed during postnatal growth and aging.