8 ng/mL (National Academy of Navitoclax datasheet Sciences, 2000, Rice, 2005 and Stern, 2005). In control populations, blood mercury concentration was reported to be 2.73 ng/mL in adults in New York City and 1 ng/mL in China. Mercury attains levels of 5.65 ng/mL (McKelvey et al., 2007) in regular fish consumption, and in workers that are regularly exposed attain levels between 7 and 10 ng/mL (Gupta et al., 1996 and Chen et al., 2005). Professional exposure to mercury vapor and release of mercury from removal of amalgam dental fillings increases its blood (18 nM; ~ 5 ng/mL) and plasma (5 nM;

~ 1.5 ng/mL) concentration (Halbach, 1995, Björkman et al., 1997, Langworth et al., 1997 and Sandborgh-Englund et al., 1998). This form of the exposure is represented by elemental mercury. Once absorved it can be oxidized into inorganic mercury (Rooney, 2007 and Björkman et al., 2007). Professional exposure also produces central nervous system alteration (Langworth et al., 1997) and tooth fillings impair kidney function (Carmignani et al., 1989). Mercury exerts its effects by combining with SH groups (Clarkson, 1972) and these actions might be the manner by which the metal exerts its effects on the cardiac myocytes (Halbach, 1989). However, the fact that mercury can concentrate

inside the cells suggests that the metal might produce effects at even lower concentrations under chronic PF-02341066 cell line exposure. We have previously reported that chronic exposure to small concentrations do produce harmful vascular effects (Furieri et al., 2011; Wiggers et al., 2008) but studies regarding cardiac function with chronic exposure to low concentrations of the metal are scarce. Given that relatively high blood levels of mercury are more likely to pose the metal as an environmental risk factor for cardiovascular diseases, we recently developed a method for producing a controlled chronic

mercury administration that attains a blood concentration of 8 ng/mL (~ 29 nM). Using a similar exposure Oxalosuccinic acid protocol, and to avoid effects of humoral and neural factors that exist in the blood, the perfused heart preparation was used. In these preparations a negative inotropic and lusitropic effect was observed in the mercury-treated group. The underlying mechanisms that could explain these findings are usually the reduction of NKA, NCX and SERCA activities (Bers, 2006). Biochemical analyses performed here showed that chronic mercury treatment reduces NKA activity, the expression of alfa-1 NKA subunit and NCX expression. Results also show reduction of SERCA expression, PLB increase and phosphorilated PLB reduction, which might lead to less calcium uptake and release. Such condition is known to reduce force development (Bers and Despa, 2006). Chronic mercury treatment reduces NKA activity leading to increased intracellular sodium concentration, which reduces NCX activity, producing a calcium overload condition.