Effects of mercury on the mechanical and electrical activity of the Langendorff-perfused rat heart
Massaroni, L.; Oliveira, E.M.; Stefanon, I.; Vassallo, D.V.
Brazilian Journal of Medical and Biological Research 25(8): 861-864
1992
ISSN/ISBN: 0100-879X PMID: 1342624 Document Number: 404306
The effects of increasing concentrations of mercury (Hg2+) chloride (0.5, 1, 2 and 10 microM) on the myocardial electromechanical activity were studied on 10 Langendorff-perfused rat hearts. Hg2+ decreased the development of isovolumic systolic pressure from 20.3 +/- 2.13 mmHg under control conditions to 6.25 +/- 1.32 mmHg at 10 microM HgCl2 (P < 0.01) (diastolic pressure = 0 mmHg). The atrial and ventricular rates also decreased at 0.5 microM, 1 microM and 2 microM HgCl2 when compared to the Hg(2+)-free solution (from 201 +/- 4 to 126 +/- 15 bpm). However, at 10 microM Hg2+ the atrial rate increased (155 +/- 19 bpm) whereas the ventricular rate did not change significantly (119 +/- 13 bpm). A delay in atrioventricular conduction occurred at 0.5 microM Hg2+ (64 +/- 4 ms in the Hg(2+)-free solution to 91 +/- 14 ms in the presence of 0.5 microM Hg2+, P < 0.05) with no further changes at higher Hg2+ concentrations. The QRS-T duration also increased as a function of increasing Hg2+ concentrations (58 +/- 5.5 ms in the Hg(2+)-free solution to 123 +/- 15 ms in the presence of 10 microM Hg2+, P < 0.01). Qualitative changes of ECG such as extrasystoles, atrial or ventricular arrhythmias and A-V blocks were also observed. The inhibitory action of Hg2+ on ATP hydrolysis and on Ca2+ and Na(+)-K+ ATPases suggested to occur in other tissues could be the mechanism responsible for the observations reported here.