Effects of Mercury on the Contractile Activity of the Right Ventricular Myocardium

Abstract

The increase in right ventricular systolic pressure observed in vivo after the administration of mercury opposes to the idea that the metal depresses the cardiac pump performance. We then investigated the effects of HgCl(2) (0.1 to 2.5 microM) on the contractile activity of the right ventricular myocardium, measuring isometric and tetanic contractions of right ventricular isolated strips, right ventricular isovolumic systolic and diastolic pressures, and the coronary perfusion pressure (0.03 to 3 microM) in constant-flow Langendorff-perfused rat hearts. The results presented here suggest that the acute effects of mercury on the right ventricular myocardium are distinct. When isolated strips of right ventricular wall are used, the contractile depression produced by mercury is manifested. However, when mercury is administered to isolated perfused hearts or in vivo this depressant effect is not revealed. The possible reasons for this behavior are the increased coronary perfusion pressure, which promotes a positive inotropic effect, manifested during the infusion of increasing concentrations of mercury, or the putative stretch of the ventricular fibers, which might cause the increment of diastolic pressure. An interesting finding is that the mechanical activity of the preparations, in which mercury is administered via coronary circulation, is not depressed and, even more, it can increase systolic pressure. However, the nature of this protective effect of coronary circulation cannot be explained by the results presented here.

Differential gene expression associated with dietary methylmercury (MeHg) exposure in rainbow trout (Oncorhynchus mykiss) and zebrafish (Danio rerio)

“…MYL2, TNNT3, TNN2 and TPM1function in the muscle contraction process, including ventricular myocardium (Margossian et al 1987; Macera et al 1992; Levine et al 1998; Moran et al 2008). It has been reported that MeHg influences heart rate and increases systolic and diastolic pressure in rat by depressing the ventricular myocardium (Cunha et al 2001; de Assis et al 2003). In the present study, GO terms of molecular function related to muscle contraction were significantly enriched, such as calcium-dependent ATPase activity, troponin I binding, and troponin C binding.…”