ANGIOTENSIN-II ACTIVATES PROGRAMMED MYOCYTE CELL-DEATH IN-VITRO

To determine whether angiotensin II (Ang II) can induce apoptosis of n eonatal ventricular myocytes, these cells were exposed to 10(-9) M Ang II for 24 h in vitro and the effects of this intervention on programm ed myocyte cell death were examined by the terminal deoxynucleotidyl t ransferase assay and DNA gel electrophoresis. Ang II resulted morpholo gically in a 2.5-fold increase in the percentage of myocytes with doub le strand cleavage of the DNA and biochemically in the formation of DN A fragments equal in size to mono- and oligonucleosomes. Moreover, Ang II stimulation was characterized by a 37% increase in resting level o f intracellular calcium and the activation of calcium-dependent endoge nous endonuclease. In contrast, pH-dependent endogenous endonuclease w as not enhanced by the addition of Ang II. Ang II-induced DNA damage w as inhibited by the AT(1) receptor antagonist, losartan. Similarly, th e calcium chelator, BAPTA-AM, prevented Ang II-mediated cell death. Co nversely, the calcium ionophore, A23187, triggered programmed cell dea th. Finally, the selective AT(2) receptor subtype blocker, PD123319, f ailed to reduce myocyte apoptosis. In conclusion, ligand binding of AT (1) receptors may initiate programmed myocyte cell death via an elevat ion in cytosolic calcium and the stimulation of calcium-dependent endo genous endonuclease. (C) 1997 Academic Press.