Studies on collagen in the experimental myocardial infarction

The healing process of myocardial infarction was studied with special reference to the production of collagen by the determinations of prolylhydroxylase (PHase) activity and contents of hydroxyproline (Hyp) of the collagen subfractions, i.e., neutral salt soluble (NSC), acid soluble (ASC) and insoluble collagens (ISC) in comparison with histologic observation of the proliferation of connective tissue in the canine heart. The contents of Hyp in NSC and ASC increased in the infarcted tissue 5 days after coronary ligation prior to its increase in ISC. The content of Hyp in NSC, which is a precursor of ASC and ISC, reached the maximal value at 7 days and that reached the maximal value in ASC 7 to 14 days after coronary ligation. ISC increased markedly after 14 days. PHase activity increased on the second day and attained to the highest at 5 to 7 days. Proliferation of fibroblasts paralleled with the increases in PHase activity and NSC, and an increase in collagen fiber did with the contents of ISC. From these results it is concluded that in the healing stage of myocardial infarction, PHase was activated earlier than the increase in immature collagen in the infarcted area which was observed 5 to 7 days after coronary ligation and was followed by the production of mature collagen after 14 days.