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

Abstract

Mercury reduces cardiac contractility and arterial pressure at micromolar concentrations. We investigated the actions of 680 ng/kg HgCl 2 on arterial pressure, heart rate (HR) and on the pressor reactivity to phenylephrine (PHE) in rats before and 1 h after HgCl 2 administration and after hexametonium, verapamil and tempol treatments. HgCl 2 increased baseline systolic (SAP) and diastolic pressure (DAP) and HR, sensitivity (pD 2) and maximal response ( E max) to PHE pressor reactivity. Hexametonium and verapamil reduced baseline pressures and HR that increased after HgCl 2 treatment. Hexametonium did not change pD 2 or E max to PHE but verapamil reduced them. These parameters increased after HgCl 2 administration. Tempol did not alter baseline pressures, HR or PHE reactivity before and after HgCl 2. Results suggest that HgCl 2 increases SAP, DAP, HR and PHE reactivity; autonomic reflexes reduces HgCl 2 action; baseline pressure level do not interfere on HgCl 2 pressor effects but free radicals seems to be involved.