title: Exposure to low mercury concentration in vivo impairs myocardial contractile function.
abstract: Increased cardiovascular risk after mercury exposure has been described but cardiac effects resulting from controlled chronic treatment are not yet well explored. We analyzed the effects of chronic exposure to low mercury concentrations on hemodynamic and ventricular function of isolated hearts. Wistar rats were treated with HgCl₂ (1st dose 4.6 μg/kg, subsequent dose 0.07 μg/kg/day, im, 30 days) or vehicle. Mercury treatment did not affect blood pressure (BP) nor produced cardiac hypertrophy or changes of myocyte morphometry and collagen content. This treatment: 1) in vivo increased left ventricle end diastolic pressure (LVEDP) without changing left ventricular systolic pressure (LVSP) and heart rate; 2) in isolated hearts reduced LV isovolumic systolic pressure and time derivatives, and β-adrenergic response; 3) increased myosin ATPase activity; 4) reduced Na+-K+ ATPase (NKA) activity; 5) reduced protein expression of SERCA and phosphorylated phospholamban on serine 16 while phospholamban expression increased; as a consequence SERCA/phospholamban ratio reduced; 6) reduced sodium/calcium exchanger (NCX) protein expression and α-1 isoform of NKA, whereas α-2 isoform of NKA did not change. Chronic exposure for 30 days to low concentrations of mercury does not change BP, heart rate or LVSP but produces small but significant increase of LVEDP. However, in isolated hearts mercury treatment promoted contractility dysfunction as a result of the decreased NKA activity, reduction of NCX and SERCA and increased PLB protein expression. These findings offer further evidence that mercury chronic exposure, even at small concentrations, is an environmental risk factor affecting heart function.
authors: Department of Physiological Sciences, Federal University of Espirito Santo, Vitoria, ES, Brazil.
authors: Lorena Barros
authors: LB
authors: Furieri
authors: Mirian
authors: M
authors: Fioresi
authors: Rogério Faustino Ribeiro
authors: RF
authors: Junior
authors: María Visitación
authors: MV
authors: Bartolomé
authors: Aurélia Araújo
authors: AA
authors: Fernandes
authors: Victoria
authors: V
authors: Cachofeiro
authors: Vicente
authors: V
authors: Lahera
authors: Mercedes
authors: M
authors: Salaices
authors: Ivanita
authors: I
authors: Stefanon
authors: Dalton Valentim
authors: DV
authors: Vassallo
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006651:Histocytochemistry; D007527:Isoenzymes; D008297:Male; D008627:Mercuric Chloride / Q000633:toxicity*; D023421:Models, Animal; D009200:Myocardial Contraction / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D019831:Sodium-Calcium Exchanger; D008627:Mercuric Chloride; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase