Induction of Apoptosis in Rat Myocardium under Anoxic Conditions

V. B. Saprunova^*, S. A. Kazimirchuk, A. A. Tonshin, L. E. Bakeeva, and L. S. Yagujinsky

Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-0338; E-mail: yag@genebee.msu.su

^* To whom correspondence should be addressed.

Received April 12, 2001; Revision received June 28, 2001

---

The effect of anoxic incubation of small slices of isolated rat hearts on respiration, internucleosomal DNA fragmentation, and mitochondrial ultrastructure was investigated. Anoxic incubation for 72 h induced apoptosis accompanied by internucleosomal DNA fragmentation and changes in respiration and mitochondrial ultrastructure. The mitochondrial population was characterized by morphological heterogeneity. In a significant part of the mitochondrial population there were signs of mitochondrial swelling and appearance of electron-dense mitochondria. Anoxia also induced the appearance of an atypical (and previously unknown) population of small electron-dense mitochondria. They were characterized by unusual localization inside electron-light mitochondria. Under anoxic conditions the inner mitochondrial membrane formed electron-dense ordered structures. All changes described here reflect two opposing processes occurring in mitochondria: apoptotic destruction and compensatory processes responsible for maintenance of mitochondria.

---

KEY WORDS: apoptosis, anoxia, cardiomyocytes, myocardial infarction, mitochondria, electron microscopy

---