Dose-Dependent Effects of Subchronic Lead Exposure on the Right Atrium and Right Ventricle of Rats: An In Vitro Investigation.

Lead poisoning remains a significant threat to both human and animal health, with cardiovascular dysfunction being one of its primary adverse effects. This study aimed to investigate the function of the right atrium and right ventricle in 12-month-old male rats exposed to 5.5, 11, and 22.88 mg/kg body weight of lead acetate, injected intraperitoneally three times a week for six weeks. Lead exposure resulted in a reduction in blood pressure (11 mg/kg b.w.) and QRS amplitude, and a lowering of the isoelectric line. Lead exposure led to a dose-dependent shift in the myosin heavy chain (MHC) ratio toward the slower β-MHC isoform in the right ventricle, whereas no changes were detected in the right atrium. We observed a dose-dependent increase in myosin regulatory light chain phosphorylation in the right ventricle and a decrease in the right atrium. In the atria, both active and passive tensions were reduced, while no significant alterations were found in the right ventricle. However, a dose-dependent slowing of the action potential was found in both atrial and ventricular myocardium. Both the right atrium and right ventricle demonstrated responses to lead exposure; however, there was a mismatch between the alterations observed in atrial and ventricular parameters. These findings suggest that the atrial and ventricular myocardium adapt differently to lead exposure, with their responses varying depending on the specific dosage of lead consumed.