Paola Zambelli Moraes

The cessation of the long-term exposure to low doses of mercury ameliorates the increase in systolic blood pressure and vascular damage in rats

&NA; This study aimed to verify whether a prolonged exposure to low‐level mercury promotes haemodynamic disorders and studied the reversibility of this vascular damage. Rats were divided into seven groups: three control groups received saline solution (im) for 30, 60 or 90 days; two groups received HgCl2 (im, first dose, 4.6 &mgr;g/kg, subsequent doses 0.07 &mgr;g/kg/day) for 30 or 60 days; two groups received HgCl2 for 30 or 60 days (im, same doses) followed by a 30‐day washout period. Systolic blood pressure (SBP) was measured, along with analysis of vascular response to acetylcholine (ACh) and phenylephrine (Phe) in the absence and presence of endothelium, a nitric oxide (NO) synthase inhibitor, an NADPH oxidase inhibitor, superoxide dismutase, a non‐selective cyclooxygenase (COX) inhibitor and an AT1 receptor blocker. Reactive oxygen species (ROS) levels and antioxidant power were measured in plasma. HgCl2 exposure for 30 and 60 days: a) reduced the endothelium‐dependent relaxation; b) increased the Phe‐induced contraction and the contribution of ROS, COX‐derived vasoconstrictor prostanoids and angiotensin II acting on AT1 receptors to this response while the NO participation was reduced; c) increased the oxidative stress in plasma; d) increased the SBP only after 60 days of exposure. After the cessation of HgCl2 exposure, SBP, endothelium‐dependent relaxation, Phe‐induced contraction and the oxidative stress were normalised, despite the persistence of the increased COX‐derived prostanoids. These results demonstrated that long‐term HgCl2 exposure increases SBP as a consequence of vascular dysfunction; however, after HgCl2 removal from the environment the vascular function ameliorates. HighlightsLong‐term exposure to low concentrations of Hg increases SBP in rats.Hg increases vascular RAS activity, oxidative stress and prostanoids from COX.The vascular damage is ameliorated after cessation of the ongoing exposure to Hg.Hg cessation decreases RAS activation and oxidative stress.