Effects of Internal Exposure to 56MnO2 Powder on Blood Parameters in Rats

Objective: The pathological effects of internal exposure to manganese dioxide-56 ((56)MnO2) radioisotope particles have been previously examined in rats. Here we further examine the effects of (56)MnO2, focusing on changes in blood parameters. Materials and Methods: Ten-week-old male Wistar rats were exposed to 3 doses of neutron-activated (56)MnO2 powder, nonradioactive MnO2 powder, or external 60Co gamma-rays (1 Gy, whole body). On days 3 and 61 postexposure, the animals were necropsied to measure organ weights and clinical blood parameters, including red blood cell and white blood cell counts; concentrations of calcium, phosphorus, potassium, and sodium; and levels of alanine aminotransferase (ALT), aspartate aminotransferase, amylase, creatinine, urea, total protein, albumin, triglycerides, high density lipoprotein, total cholesterol, and glucose. Results: In the (56)MnO2-exposed animals, accumulated doses were found to be highest in the gastrointestinal tract, followed by the skin and lungs, with whole-body doses ranging from 41 to 100 mGy. There were no (56)MnO2 exposure-related changes in body weights or relative organ weights. The ALT level decreased on day 3 and then significantly increased on day 61 in the (56)MnO2-exposed groups. There were no exposure-related changes in any other blood parameters. Conclusion: Although the internal doses were less than 100 mGy, internal exposure of (56)MnO2 powder showed significant biological impacts.