Angiotensin II activates programmed myocyte cell death in vitro

To determine whether angiotensin II (Ang II) can induce apoptosis of neonatal ventricular myocytes, these cells were exposed to 10(-9) M Ang II for 24 h in vitro and the effects of this intervention on programmed myocyte cell death were examined by the terminal deoxynucleotidyl transferase assay and DNA gel electrophoresis. Ang II resulted morphologically in a 2.5-fold increase in the percentage of myocytes with double strand cleavage of the DNA and biochemically in the formation of DNA fragments equal in size to mono- and oligonucleosomes. Moreover, Ang II stimulation was characterized by a 37% increase in resting level of intracellular calcium and the activation of calcium-dependent endogenous endonuclease. In contrast, pH-dependent endogenous endonuclease was not enhanced by the addition of Ang II. Ang II-induced DNA damage was inhibited by the AT1 receptor antagonist, losartan. Similarly, the calcium chelator, BAPTA-AM, prevented Ang II-mediated cell death. Conversely, the calcium ionophore, A23187, triggered programmed cell death. Finally, the selective AT2 receptor subtype blocker, PD123319, failed to reduce myocyte apoptosis. In conclusion, ligand binding of AT1 receptors may initiate programmed myocyte cell death via an elevation in cytosolic calcium and the stimulation of calcium-dependent endogenous endonuclease.