title: Intracellular calcium, DNase activity and myocyte apoptosis in aging Fischer 344 rats.
abstract: Myocyte apoptosis increases with age in Fischer 344 rats, but the multiple molecular events implicated in this phenomenon remain to be identified. Several defects involving Ca2+ homeostasis, pH, and the expression of p53 and genes of the Bcl-2 protein family may contribute to the activation of myocyte death. Therefore, changes in intracellular pH, cytosolic Ca2+, DNase I and DNase II were measured in myocytes isolated by enzymatic digestion from rats of different ages. Moreover, the expression of p53, Bcl-2 and Bax in these cells was determined. Measurements of intracellular pH by BCECF fluorescence at 3, 12 and 24 months showed that this parameter did not change with age: 3 months, 7.20+/-0.05; 12 months, 7.21+/-0.07; 24 months, 7.18+/-0.09. In contrast, diastolic Ca2+ determined by the Fura 2-AM method increased progressively from 99.8+/-1.9 nm at 3 months to 136.3+/-9.6 nm at 24 months (P<0.001). Concurrently, DNase I activity evaluated by plasmid digestion assay in myocytes increased 3.2-fold from 3 to 24 months (P<0.02). Conversely, pH-dependent-DNase II remained essentially constant with age. Western blotting performed on ventricular myocytes did not detect significant changes in p53, Bax and Bcl-2 proteins with age. Similarly, immunocytochemically, the fraction of myocytes labeled by p53, Bax and Bcl-2 did not change from 3 to 24 months. In conclusion, myocyte aging is characterized by an increase in diastolic calcium which may activate DNase I triggering apoptosis, independently from the expression of p53, Bax and Bcl-2 in the cells.
authors.affiliation: Department of Medicine, New York Medical College, Valhalla, NY, 10595, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Nitahara
authors.forename: W
authors.initials: W
authors.lastname: Cheng
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: B
authors.initials: B
authors.lastname: Li
authors.forename: A
authors.initials: A
authors.lastname: Leri
authors.forename: P
authors.initials: P
authors.lastname: Li
authors.forename: D
authors.initials: D
authors.lastname: Mogul
authors.forename: S R
authors.initials: SR
authors.lastname: Gambert
authors.forename: J
authors.initials: J
authors.lastname: Kajstura
authors.forename: P
authors.initials: P
authors.lastname: Anversa
mesh_terms: D000375:Aging / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000378:metabolism; D015870:Gene Expression; D019254:Genes, bcl-2; D016158:Genes, p53; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D011916:Rats, Inbred F344; D051028:bcl-2-Associated X Protein
chemical_list: C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D003851:Deoxyribonucleases; D004706:Endodeoxyribonucleases; D003850:Deoxyribonuclease I; C019329:deoxyribonuclease II; D002118:Calcium