Inhibitors of poly (ADP-ribose) synthetase protect rat cardiomyocytes against oxidant stress

Objective: inhibitors of poly (ADP-ribose) synthetase (PARS) activity reduc e the infarct size caused by regional myocardial ischaemia and reperfusion in the rabbit and rat in vivo. The mechanism of action of these inhibitors is unclear. Here we investigate the effects of the PARS inhibitor 3-aminobe nzamide (3-AB) on infarct size caused by ischaemia and reperfusion of the i solated, perfused heart of the rat. We also investigate the role of PARS in the hydrogen peroxide-mediated cell injury/necrosis in rat cardiac myoblas ts. Methods: Rat isolated hearts perfused at constant pressure (80 mmHg) we re subjected to 35 min of regional ischaemia and 2 h of reperfusion. Infarc t size was determined at the end of the experiment using nitro-blue tetrazo lium. 3-AB (300 mu M) or 3-aminobenzoic acid (3-ABA, 300 mu M) were infused during the reperfusion period. Rat cardiac myoblasts (H9c2 cells) were pre incubatcd with the PARS inhibitors, 3-AB, nicotinamide (Nic) or 1,5-dihydro xyisoquinoline (ISO) or the inactive analogues 3-ABA or nicotinic acid (Nic A) prior to exposure with hydrogen peroxide (1 mM). Cell injury was assesse d by measuring mitochondrial respiration and cell necrosis by measuring the release of LDH. PARS activity was determined by measuring the incorporatio n of NAD into nuclear proteins. Results: Regional ischaemia and reperfusion of the isolated rat heart resulted in an infarct size of 54% which was red uced by 3-AB, but not by 3-ABA. Exposure of rat cardiac myoblasts to hydrog en peroxide caused an increase in PARS activity and cell injury necrosis wh ich was attenuated by pretreatment with the PARS inhibitors. Conclusion: In hibition of the activity of PARS attenuates the cell death associated with oxidant stress in rat cardiac myoblasts and heart. (C) 1999 Elsevier Scienc e B.V. All rights reserved.