NO production and eNOS phosphorylation induced by epinephrine through the activation of beta-adrenoceptors

Epinephrine plays a key role in the control of vasomotor tone; however, the participation of the NO/cGMP pathway in response to beta-adrenoceptor activation remains controversial. To evaluate the involvement of the endothelium in the vascular response to epinephrine, we assessed NO production, endothelial NO synthase phosphorylation, and tissue accumulation of cGMP in the perfused arterial mesenteric bed of rat. Epinephrine elicited a concentration-dependent increase in NO (EC(50) of 45.7 pM), which was coupled to cGMP tissue accumulation. Both NO and cGMP production were blocked by either endothelium removal (saponin) or NO synthase inhibition (N(omega)-nitro-L-arginine). Blockade of beta(1)- and beta(2)-adrenoceptors with 1 microM propranolol or beta(3)-adrenoceptor with 10 nM SR 59230A displaced rightward the concentration-NO production curve evoked by epinephrine. Selective stimulation of beta(1)-, beta(2)-, or beta(3)-adrenoceptors also resulted in NO and cGMP production. Propranolol (1 microM) inhibited the rise in NO induced by isoproterenol or the beta(2)-adrenoceptor agonists salbutamol, terbutaline, or fenoterol. Likewise, 10 nM SR 59230A reduced the effects of the beta(3)-adrenoceptor agonists BRL 37344, CGP 12177, SR 595611A, or pindolol. The NO production induced by epinephrine and BRL 37344 was associated with the activation of the phosphatidylinositol 3-kinase/Akt pathway and phosphorylation of eNOS in serine 1177. In addition, in anaesthetized rats, bolus administration of isoproterenol, salbutamol, or BRL 37344 produced NO-dependent reductions in systolic blood pressure. These findings indicate that beta(1)-, beta(2)-, and beta(3)-adrenoceptors are coupled to the NO/cGMP pathway, highlighting the role of the endothelium in the vasomotor action elicited by epinephrine and related beta-adrenoceptor agonists.