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

Objective: The pathological effects of internal exposure to manganese dioxide-56 ((MnO2)-Mn-56) radioisotope particles have been previously examined in rats. Here we further examine the effects of (MnO2)-Mn-56, focusing on changes in blood parameters. Materials and Methods: Ten-week-old male Wistar rats were exposed to 3 doses of neutron-activated (MnO2)-Mn-56 powder, nonradioactive MnO2 powder, or external Co-60 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 (MnO2)-Mn-56-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 (MnO2)-Mn-56 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 (MnO2)-Mn-56-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 (MnO2)-Mn-56 powder showed significant biological impacts.