title: Cyclical mechanical stretch-induced apoptosis in myocytes from young rats but necrosis in myocytes from old rats.
abstract: Mechanical load as stimulus for apoptosis and necrosis could be responsible for the loss of cardiomyocytes. Ventricular myocytes from young (3 mo) and old (14-24 mo) rats underwent cyclical mechanical stretch (CMS; 5% elongation, 1 Hz) for 24 h. Spontaneous apoptosis was in myocytes from young rats 0.33 +/- 0.12% and from old rats 1.05 +/- 0.35% [Tdt-mediated dUTP nick-end labeling (TUNEL) assay]; associated with a decrease of Bcl-2. CMS increased the apoptosis to 0.58 +/- 0.18% in myocytes from young rats. Western blot analysis showed that CMS reduced Bcl-2 and increased p53 (young rats). Bax was not changed by CMS. These were confirmed by cytochrome c release (31 +/- 13%) and by the enrichment of cytosolic nucleosomes (11 +/- 8%). CMS did not influence the apoptosis in myocytes from old rats (TUNEL assay, Bcl-2, Bax, or p53). CMS did not cause necrosis in myocytes from young rats. CMS increased the number of necrotic cells by showing the cell membrane rupture in myocytes from old rats (50 +/- 13% 5-hexadecanoylaminofluorescein-positive and 38 +/- 6% propidium iodide-positive cells) as well as by measuring the lactate dehydrogenase release. The results suggest that CMS-induced apoptosis in myocytes of young rats but necrosis in myocytes from old rats, which could be attributed to more stress sensitivity of cells from old rats.
authors.affiliation: Department of Physiology, Martin-Luther-University Halle/Wittenberg, 6 Magdeburger St., D-06097 Halle, Germany. britta.husse@medizin.uni-halle.de
authors.forename: B
authors.initials: B
authors.lastname: Husse
authors.forename: A
authors.initials: A
authors.lastname: Sopart
authors.forename: G
authors.initials: G
authors.lastname: Isenberg
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D006352:Heart Ventricles; D032383:Myocytes, Cardiac / Q000473:pathology* / Q000502:physiology*; D009336:Necrosis; D010507:Periodicity; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D013314:Stress, Mechanical; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53