OBJECTIVETo observe the vasodilating effect of adrenomedullin 2 (ADM2) by antagonizing angiotensin 1 (Ang II), and to explore its mechanism.

METHODSEighteen male, 180-200 g SD rats were randomly divided into 3 groups (n = 6): control group, Ang II (150 ng/(kg x min)) group and Ang II (150 ng/(kg x min)) + ADM2(500 ng/(kg x h)) group. Mini-osmotic pumps filled with peptide were implanted in the back of rats subcutaneously. After two weeks, the blood pressure was measured by the way of carotid intubation. The plasma was collected for the detection of nitric oxide (NO) content and the activity of endothelial nitric oxide synthase (eNOS). The in situ oxidation of fluorescent dye dihydroethidium (DHE) was used for detecting superoxide in rat arteries. The rat isolated arterial rings were made for studying the vasodilating effect of ADM2. Human umbilical vein endothelial cell line EA. hy 926 cells were cultured and their intracellular reactive oxygen species (ROS) were evaluated by probe DCFH-DA.

RESULTSADM2 dramatically decreased the blood pressure in angiotensin II-induced hypertension rat model, enhanced plasma NO content and the activity of eNOS and reduced superoxide formation in vessel walls. ADM2 also induced relaxation of the vascular rings preconstricted by Ang II in a concentration-dependent and endothelium-dependent manner. In cultured vascular endothelium, ADM2 ameliorated the ROS generation induced by Ang II.

CONCLUSIONAdrenomedullin 2 relaxed blood vessels by antagonizing angiotensin II-induced oxidative stress and improving the vascular endothelial function.