Small doses of mercury increase arterial pressure reactivity to phenylephrine in rats

Environmental Toxicology and Pharmacology 24 (2007) 92–97

Small doses of mercury increase arterial pressure reactivity to phenylephrine in rats
Adriana Caiado Machado a , Alessandra Sim˜ o Padilha a , Giulia Alessandra Wiggers a , a a , Ivanita Stefanon a,b , Dalton Valentim Vassallo a,b,∗
Fabiana Dayse Magalh˜ es Siman a a

Department of Physiological Sciences, Federal University of Espirito Santo, Vitoria, ES, Brazil b Health Science Center of Vit´ ria-EMESCAM, Vitoria, ES, Brazil o Received 7 November 2005; accepted 12 February 2007
Available online 21 April 2007

Abstract
Mercury reduces cardiac contractility and arterial pressure at micromolar concentrations. We investigated the actions of 680 ng/kg HgCl2 on arterial pressure, heart rate (HR) and on the pressor reactivity to phenylephrine (PHE) in rats before and 1 h after HgCl2 administration and after hexametonium, verapamil and tempol treatments. HgCl2 increased baseline systolic (SAP) and diastolic pressure (DAP) and HR, sensitivity (pD2 ) and maximal response (Emax ) to PHE pressor reactivity. Hexametonium and verapamil reduced baseline pressures and HR that increased after HgCl2 treatment. Hexametonium did not change pD2 or Emax to PHE but verapamil reduced them. These parameters increased after HgCl2 administration.
Tempol did not alter baseline pressures, HR or PHE reactivity before and after HgCl2 . Results suggest that HgCl2 increases SAP, DAP, HR and
PHE reactivity; autonomic reflexes reduces HgCl2 action; baseline pressure level do not interfere on HgCl2 pressor effects but free radicals seems to be involved.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Mercury; Pressure reactivity; Arterial pressure; Phenylephrine

1. Introduction
Acute intravenous administration of Hg2+ produces important hemodynamic changes. The main effect is a progressive decrease of arterial blood pressure (ABP) associated with the reduction of heart rate (HR) (Rhee and Choi, 1989;