Naringin promotes positive inotropism in atrial tissue through β-AR/PKA-dependent pathway

Naringin is a flavonoid glycoside found in citrus fruits and grapes with wide range of therapeutic actions. We aimed to study the inotropic effect naringin on rat-isolated atria, dissecting intracellular mechanisms involved this response. Concentration-response curves (0.003-6 mM) were obtained before after pre-incubation selective antagonists. Our results showed that presented biphasic response, positive at low middle concentrations (0.003-2.0 mM), negative high (above 3 mM). Pre-incubation propranolol or atenolol (β-adrenergic receptors antagonists, β-AR), H89 (protein kinase-A inhibitor, PKA), nifedipine (L-type Ca2+ channel blocker), ryanodine (ryanodine receptor inhibitor) fully abolished induced by naringin. Pre-treatment animals reserpine, catecholamine-depleting drug, also prevented increase atrial contractility evoked Altogether, we show causes isolated atria through β-AR/PKA-dependent pathway.