RESUMEN
<p><b>OBJECTIVE</b>To observe the effects of manganese sulfate on blood pressure, myocardial ultrastructure and heart organ index of rats.</p><p><b>METHODS</b>Forty male SPF SD rats were randomly divided into 4 groups: control group (0 mg/kg), 5 mg/kg dose group, 15 mg/kg dose group and 25 mg/kg dose group, 10 rats each group. Intraperitoneal injection was performed for six months, by five times each week, the rat blood pressure was measured by tail cuff method, and the heart organ index of the rats was computed. Three rats were selected from each group randomly, and the myocardial ultrastructure of the rats was observed by using transmission electron microscopy (TEM). The BMD and BMDL between manganese sulfate injected dose and the rats heart organ index were evaluated by BMD (Benchmark Dose).</p><p><b>RESULTS</b>There was no significant of blood pressure between the experimental group and the control group (P > 0.05).The heart organ indexes of the four groups were 0.24% ± 0.10%, 0.25% ± 0.02%, 0.26% ± 0.02%, and 0.24% ± 0.02%. Statistical significance of heart organ indexes was found between the 15 mg/kg dose group and the control group (P < 0.05). Observed by TEM, we found that-different degrees of mitochondrial crest fracture or disappear, mitochondria swelling, hydropic change and myocardial fibers degeneration happened in the rats of the three exposed groups, but not the control group. The BMD and BMDL were calculated as 9.33 mg/kg and 4.28 mg/kg in the study of manganese sulfate injected dose and the rats heart organ index.</p><p><b>CONCLUSION</b>Chronic manganese poisoning can lead to myocardial mitochondria superfine lesions, myocardial fiber damage and heart organ index change in rats.</p>