CONICET | Buscador de Institutos y Recursos Humanos

The beneficial or deleterious role of endogenous catecholamines released during ischemia on post-ischemic myocardial contractile recovery is still a matter of discussion. We aimed to clarify this issue by examining, in perfused rat hearts submitted to ischemia/reperfusion (20/30 min), the effects of cardiac catecholamine depletion (5 mg/kg reserpine, 24 h before sacrifice or 75 mg/kg 6-OH dopamine, 3 times/week, before sacrifice) and of alfa1- and beta-adrenergic receptors blockade (perfusion of 1 ìM prazosin and 1 ìM propranolol, respectively), on the contractile recovery after ischemia. Free radical generation during reperfusion was evaluated by measuring lipid peroxidation by thiobarbituric acid reactive substance (TBARS). At the end of reperfusion, contractile recovery, evaluated by the maximal rate of pressure development (+dP/dt), was significantly increased by depletion of catecholamines from 55 ± 10% (n = 7) to 87 ± 4% (reserpine, n = 8) and 95 ± 3% (6-OH dopamine, n = 4). Prazosin significantly decreased the recovery of +dP/dt to 21 ± 5% (n = 5); suggesting a beneficial effect of alfa1-adrenergic stimulation on the post-ischemic contractile recovery. In the presence of propranolol, the contractile recovery was rather variable. On average, the results showed that this blocker did not modify +dP/dt recovery (51 ± 8%, n = 13). Similar results were obtained when left ventricular developed pressure was used to evaluate the contractile recovery. Catecholamine depletion significantly decreased TBARS measured after 30 min of reperfusion from 29.6 ± 2.7 (n = 9) to 22.6 ± 1.7 (n = 7) nmol/g ventricular tissue. These results suggest a dual effect of catecholamine release: (1) a detrimental one independent of the adrenergic receptors stimulation and which might be mediated by the increase in oxidative stress; (2) a beneficial one, which seems to be mediated by alfa1-adrenergic stimul

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