Dietary β-adrenoceptor agonists have a persistent effect on nitric oxide synthesis in rat cultured smooth muscle cells

Abstract

Several compounds including lipopolysaccharide and sympathomimetics stimulate the expression of the inducible nitric oxide synthase in vascular smooth muscle cells. We evaluated the effect of clenbuterol on nitric oxide (NO) production by vascular smooth muscle cells of the rat aorta in culture. Wistar rats were divided into three diet groups (control, clenbuterol and washout). Aortic vascular smooth muscle cells from rats from these 3 diet groups were cultured in the presence and absence of lipopolysaccharide and/or β-adrenoceptor agonists. NO release was measured by Griess reagent. Clenbuterol or salbutamol added to cells from control rats potentiated lipopolysaccharide-induced NO release. Cells from rats fed on clenbuterol, in a medium without β-adrenoceptor agonists, showed a similar potentiation, even after a 10-day washout period. The addition of β-adrenoceptor agonists to the latter cells did not increase NO production. N G-Nitro- l-arginine decreased nitrite production in lipopolysaccharide-stimulated cells. Our results demonstrate that dietary clenbuterol has a persistent `ex vivo' effect on lipopolysaccharide-induced NO production by cultured vascular smooth muscle cells.