Intracellular calcium, DNase activity and myocyte apoptosis in aging Fischer 344 rats

James A. Nitahara, Wei Cheng, Yu Liu, Baosheng Li, Annarosa Leri, Peng Li, Doug Mogul, Steven R. Gambert, Jan Kajstura, Piero Anversa

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)519-535
Number of pages17
JournalJournal of Molecular and Cellular Cardiology
Issue number3
StatePublished - Mar 1998
Externally publishedYes


  • Bcl-2 and Bax expression in myocytes
  • Cytosolic Ca transients
  • DNA laddering in myocytes
  • DNase I and DNase II
  • Intracellular pH
  • p53

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine


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