Background
and Objective: Increased production and industrial application of manganese oxide
(MnO2) nano and microparticles have led to increased human contact
with these particles. In this study, the biodistribution of manganese in rat
liver was studied after chronic administration of two MnO2
particles. Also, the effect of these particles was studied on body weight gain
and liver function tests of rats.   Materials
and Methods: Male wistar rats were weighted and subcutaneously treated with
100 (μg/kg) nano- or micro-particles of MnO2 every two weeks for 14
weeks. Blood samples are taken directly from the heart of the rats (n=5) at the
same times. The Mn level in samples of rat hepatic tissue was determined by
ICP-MS. Serum levels of total protein, albumin, bilirubin, activities of
transaminases, lactate dehdrogenase and alkaline phosphatase were measured by
autoanalyzer.   Results: Rate of
body weight gain in rats of nano group was significantly faster and in micro
group rats was slower than control (p < 0.05). The hepatic Mn biodistribution,
accumulation and bioclearance in nanoparticles group were different from
microparticles group. The levels of total protein, albumin, bilirubin and
alkaline phosphatase activity increased, while transaminease enzymes and
lactate dehyrogenase activities decreased in serum of both groups (p < 0.05).   Conclusion: The
chronic administration of MnO2 nano- and microparticles casued
manganese accumulation in hepatic tissue. The strong oxidizing property of both
MnO2 particles and their binding with some hepatic enzymes can be
main causes of liver dysfunction.