Abstract

Objective: Exposure to low levels of lead acetate can induce hypertension in both humans and experimental animals. The exact mechanisms of lead-induced hypertension are not well understood, but its pathogenesis could be explained by the changes in heart rate and contractility. Materials and Methods: in the present study, the effects of exposure to 100 ppm of lead in drinking water (for periods of 4, 8, and 12 weeks) on blood pressure and some physiologic parameters (eg, electrocardiography ECG, heart rate HR, cardiac contractility, and coronary flow) of isolated beating rat heart was investigated using the Langendorff isolated heart apparatus. The isolated hearts were perfused with Krebs-Henseleit solution (37 degrees C; pH 7.4; gassed with 95% O-2 + 5% CO2). All data were digitized by a software program for further analysis. Results: The blood pressure in the 8- and 12-week lead-exposed groups was significantly increased as compared to the control group. The ECG showed arrhythmias and conduction abnormalities only in the late phases of exposure 0 2 weeks). The HR and contractility were significantly higher in the 8- and 12-week lead-treated rats but not in the 4-week group. No significant changes were observed in coronary flow. Conclusion: These results indicate that: 1) low levels of lead exposure do not significantly affect the ECG in the early phase, 2) low levels of lead exposure causes ECG changes in the late phases of exposure, and 3) this level of lead exposure can increase HR and cardiac contractility but has no effect on coronary flow.