Myocardial histoanatomical alterations in STZ-induced DM rabbits. The heart sections of STZ-induced rabbits 2 weeks following diabetes induction showed mild edema and minor vacuolization in the cytoplasm. After 4 weeks, obvious edema, more vacuolization in the cytoplasm, and a few hemorrhages were observed. Eight weeks later, in addition to moderate vacuolization and hemorrhage, histiocyte proliferation and interstitial fibrosis appeared. After 12 weeks, degenerative changes in the nuclei, severe histiocyte proliferation, interstitial fibrosis, and collagen deposits were observed.