Angiotensin II induces apoptosis of adult ventricular myocytes in vitro

To determine whether angiotensin II (Ang II) activates the suicide program of myocytes, primary cultures of adult rat ventricular myocytes were exposed to 10(-9) M of Ang II, for 24 h. Ang II resulted in a five-fold increase in programmed myocyte cell death (PMCD) documented by the terminal deoxgnucleotidyl transferase assay and confirmed by DNA agarose gel electrophoresis. Ang II stimulation was associated with translocation of the epsilon and delta isoforms of protein kinase C (PKC) which was coupled with an increase in cytosolic Ca2+ in the cells. The PKC inhibitor chelerythrine abolished Ang II-mediated increases in cytosolic Ca2+ and PMCD. Similarly, pretreatment of cells with the intracellular Ca2+ chelator BAPTA/AM inhibited the formation of DNA strand breaks. Conversely the Ca2+ ionophore A23187 markedly increased PMCD, Finally, the AT(1) receptor antagonist, losartan, completely blocked Ang II-induced PMCD, whereas the AT(2) receptor antagonist, PD123319, did not attenuate this phenomenon. In conclusion, ligand binding of AT(1) receptors on myocytes triggers PMCD by a mechanism involving PKC-mediated increases in cytosolic calcium, which result in internucleosomal DNA fragmentation. (C) 1997 Academic Press Limited.