Abstract
Right ventricle systolic dysfunction is a major risk factor for death and heart failure after myocardial infarction (MI). Heavy metal exposure has been associated with the development of several cardiovascular diseases, such as MI. The aim of this study was to investigate whether chronic exposure to low doses of mercury chloride (HgCl2) enhances the functional deterioration of right ventricle strips after MI. Male Wistar rats were divided into four groups: Control (vehicle); HgCl2 (exposure during 4 weeks- 1st dose 4.6 µg/kg, subsequent dose 0.07 µg/kg/day, i.m. to cover daily loss); MI surgery induced and HgCl2-MI groups. One week after MI, the morphological and hemodynamic measurements and isometric tension of right ventricle strips were investigated. The chronic HgCl2 exposure did not worsen the injury compared with MI alone in the morphological or hemodynamic parameters evaluated. At basal conditions, despite similar maximum isometric force at L-max, relaxation time was increased in the MI group but unaffected in the HgCl2-MI compared to the Control group. Impairment of the sarcoplasmic reticulum (SR) function and reduction in the sarcolemmal calcium influx were observed in MI group associated with SERCA2a reduction and increased PLB protein expression. Induction of MI in chronic HgCl2 exposed rats did not cause any alteration in the developed force at L-max, lusitropic function or −dF/dt except for a tendency of a reduction SR function. These findings could be partially explained by the normalization in the sarcolemmal calcium influx and the increase in NCX protein expression observed only in this group. These results suggest that chronic exposure to low doses of HgCl2 prevents the impaired SR function and the reduced sarcolemmal calcium influx observed in MI likely by acting on NCX, PLB and SERCA2a protein expression.
Highlights
Myocardial Infarction (MI) is currently the leading cause of morbidity and mortality worldwide, costing the public health system millions every year [1]
Chronic exposure to HgCl2 alone did not change the overall morphological and hemodynamic measurements evaluated when compared to Control group (p.0.05) Because these results are similar to the control group, they will not be included in the body of results but presented as supporting information (Table S1)
Our results suggest that chronic exposure to HgCl2 plus MI caused less damage to the contractile function of the right ventricle strips when compared with MI alone, and this might be associated with an increase in sarcolemmal calcium influx
Summary
Myocardial Infarction (MI) is currently the leading cause of morbidity and mortality worldwide, costing the public health system millions every year [1]. After a few hours post-MI, the ischemic process in the myocardium begins to cause deleterious effects on the contractile function of the heart [8]. In isolated heart models, acute MI impaired both the force development and the contractile index [9]. Right ventricle dysfunction has been considered as an independent predictor of mortality and predicts the development of HF in patients with left ventricle dysfunction [12]. It is very important to study the alterations in right ventricular function after acute left ventricle MI to elucidate the mechanisms involved in this process
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