Chronic dietary L-arginine down-regulates adenosine receptor and nitric oxide synthase expression in rat heart

L-Arginine increases myocardial nitric oxide production. Nitric oxide mediates many of the cardiovascular actions of adenosine and modulates adenosine metabolism. In this study, we examined the effect of chronic l-arginine (5%) intake on cardiac nitric oxide synthase (NOS) and adenosine receptor expression and cardiac function in rat Langendorff-isolated perfused hearts. Our results show that 4-week chronic l-arginine ingestion increases the weight of rat hearts by 17.6% (P 0.05); however, noradrenaline-mediated increases in contractility and myocardial oxygen consumption were reduced. Vasodilator responses to 5′-N-ethylcarboxamidoadenosine (NECA) were reduced in hearts from l-arginine-treated rats and the NOS inhibitor Nω-nitro-l-arginine methyl ester (3 μM) did not inhibit responses to NECA. In conclusion, 4-week dietary supplementation of l-arginine reduced the expression of cardiac adenosine receptors and NOSs with a subsequent decrease in noradrenaline-stimulated cardiac function and adenosine receptor-mediated coronary vasodilation