[Histochemical and histoenzymatic study of experimental myocardial infarction in the rat by temporary and permanent ligation of the left coronary artery (author's transl)].

The evolution of experimental myocardial infarction in the Rat with or without revascularization has been studied histochemically and histoenzymatically in 56 animals sacrified after 1, 6, 12, 24, 48 hrs and 7 days. Following permanent ischemis (14 animals), there appeared an extended transversal infarction marked by the complete disappearance of all phosphorylase activity (P-ase) after the first hour. During the first 6 hrs, changes appeared in succinodeshydrogenase (SHD) and cytochrome oxydase (Cyt-Ox). Glucose-6-phosphodeshydrogenase (G6PDH) presisted until lysis of the necrotic focus. It was possible to define a perinecrotic marginal area in which Pase activity is absent and SDH is granular "G3 in nature, characterized by continuous remodeling in the first 48 hrs. Following temporary ischemia (42 animals) the evolution was marked by rapid tissue reactions and early regression of the marginal zones. After 48 hrs and 7 days of survival, the planimetric evaluation of the infarcted area shows a definite reduction in the size of the infarctus in 50% of cases following removal of the ligature after 6 hrs, and in 66% of cases following removal of the ligature after 1 hr. It would appear probable that the revitalization of certain myocardial areas may extend from the marginal zones as is suggested by the reappearance in these zones several hrs after revascularization of P-ase and SDH activity. On the other hand, it is also true that the early restoration of blood flow does not always prevent the occurrence of an extended infarction. Certain recent observations have shown microcirculatory changes which are secondary to anoxia and should be studied further.