Effects of mercury on the arterial blood pressure of anesthetized rats

Abstract

The available data suggests that hypotension caused by Hg 2+ administration may be produced by a reduction of cardiac contractility or by cholinergic mechanisms. The hemodynamic effects of an intravenous injection of HgCl 2 (5 mg/kg) were studied in anesthetized rats (N = 12) by monitoring left and right ventricular (LV and RV) systolic and diastolic pressures for 120 min. After HgCl 2 administration the LV systolic pressure decreased only after 40 min (99 ± 3.3 to 85 ± 8.8 mmHg at 80 min). However, RV systolic pressure increased, initially slowly but faster after 30 min (25 ± 1.8 to 42 ± 1.6 mmHg at 80 min). Both right and left diastolic pressures increased after HgCl 2 treatment, suggesting the development of diastolic ventricular dysfunction. Since HgCl 2 could be increasing pulmonary vascular resistance, isolated lungs (N = 10) were perfused for 80 min with Krebs solution (continuous flow of 10 ml/min) containing or not 5 µM HgCl 2 . A continuous increase in pulmonary vascular resistance was observed, suggesting the direct effect of Hg 2+ on the pulmonary vessels (12 ± 0.4 to 29 ± 3.2 mmHg at 30 min). To examine the interactions of Hg 2+ and changes in cholinergic activity we analyzed the effects of acetylcholine (Ach) on mean arterial blood pressure (ABP) in anesthetized rats (N = 9) before and after Hg 2+ treatment (5 mg/kg). Using the same amount and route used to study the hemodynamic effects we also examined the effects of Hg 2+ administration on heart and plasma cholinesterase activity (N = 10). The in vivo hypotensive response to Ach (0.035 to 10.5 µg) was reduced after Hg 2+ treatment. Cholinesterase activity (µM h -1 mg protein -1 ) increased in heart and plasma (32 and 65%, respectively) after Hg 2+ treatment. In conclusion, the reduction in ABP produced by Hg 2+ is not dependent on a putative increase in cholinergic activity. HgCl 2 mainly affects cardiac function. The increased pulmonary vascular resistance and cardiac failure due to diastolic dysfunction of both ventricles are factors that might contribute to the reduction of cardiac output and the fall in arterial pressure. Correspondence

Methylmercury and elemental mercury differentially associate with blood pressure among dental professionals

“…The effect of elemental mercury on cardiovascular function in humans is not well characterized, but there are laboratory animal studies that may shed light on our findings. The general trends observed in our elemental mercury-exposed male population are consistent with animal studies that have reported that high doses of inorganic mercury cause depressed arterial systolic pressure (Massaroni et al, 1995; Rhee and Choi, 1989; Rossoni et al, 1999). Differences between elemental mercury and methylmercury effects may be realized at the cellular level.…”

“…Though several animal studies have documented that elemental mercury may decrease myocardial mechanical activity, depress heart rate, promote heart arrhythmias, and cause hypotension (Massaroni et al, 1995; Rhee and Choi, 1989; Rossoni et al, 1999), to our knowledge these relationships have not been investigated in an epidemiological study. Accordingly, the goal of this study was to increase understanding of the association between mercury exposure (both methylmercury and elemental mercury) and blood pressure in a cohort of dental professionals.…”

Modulation of Vasodilator Response via the Nitric Oxide Pathway after Acute Methyl Mercury Chloride Exposure in Rats

“…Mercury per se is reported to induce an endothelial-dependent vasorelaxation and alter structure and function of vascular endothelial cells [7]. Mercury at 5 mg/kg, iv is reported to induce hypotension in rats [23]. …”

Toxic Effects of Mercury on the Cardiovascular and Central Nervous Systems

“…Moreover, Naganuma et al [124] reported that acute exposure to HgCl 2 (680 ng/kg) increased blood pressure, heart rate, and vascular reactivity to phenylephrine in rats; this increased reactivity seems to depend on an increased generation of free radicals. Perfused hearts from animals exposed acutely to HgCl 2 showed a reduction in left ventricular systolic pressure, heart rate, and atrioventricular conduction delay [125, 126]. …”