ANGIOTENSIN-II INDUCES APOPTOSIS OF ADULT VENTRICULAR MYOCYTES IN-VITRO

To determine whether angiotensin II (Ang II) activates the suicide pro gram of myocytes, primary cultures of adult rat ventricular myocytes w ere 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 t he terminal deoxgnucleotidyl transferase assay and confirmed by DNA ag arose gel electrophoresis. Ang II stimulation was associated with tran slocation 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 cy tosolic Ca2+ and PMCD. Similarly, pretreatment of cells with the intra cellular 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 A ng II-induced PMCD, whereas the AT(2) receptor antagonist, PD123319, d id not attenuate this phenomenon. In conclusion, ligand binding of AT( 1) receptors on myocytes triggers PMCD by a mechanism involving PKC-me diated increases in cytosolic calcium, which result in internucleosoma l DNA fragmentation. (C) 1997 Academic Press Limited.