Effect of Lead, Cadmium, and Their Combination on the Heart Rate Regulation in Nonlinear Rats

We studied heart rate variability (HRV) and the concentrations of heavy metals in the heart tissue after 14-fold peroral administration of heavy metal salts: lead acetate (50 mg/kg), cadmium chloride (5 mg/kg), and their combination. After administration of lead, its concentration in the myocardium exceeded the control values by 1.2 times or did not change in case of combination with cadmium; after administration of cadmium, its concentration in the myocardium exceeded the control value by 6.1 times or by 2 times after combined administration. After lead administration, a moderate increase in HR, low values of stress and centralization indices, and an increase in the power in all ranges of the HRV spectrum were recorded. After cadmium intoxication, a tendency to a decrease in heart rhythm variability, a moderate increase in HR, stress and centralization indices, and an increase in the contribution of VLF waves in the HRV spectrum were observed. After combined administration, a pronounced increase in HR and stress index and a moderate increase in the centralization of heart rhythm control were recorded, which was similar to changes in HRV observed after administration of cadmium alone. In the experiment, the concentration of cadmium in the myocardium increased to a much greater extent than the concentration of lead. After lead administration, the autonomous type of regulation persisted and parasympathetic influences increased. Cadmium apparently acts as a stress factor and increases the role of sympathoadrenal influences and central ergotropic structures in the heart rhythm regulation.