Bioaccumulation and Locomotor Effect of Manganese Dust in Rats

Abstract

The primary goal of this study is to determine the effects of Mn exposure via inhalation. The bioaccumulation of Mn in different organs and tissues, the alteration of biochemical parameters, and the locomotor activity were assessed. A group of 26 male Sprague-Dawley rats (E) were exposed to 3750 microg/m(3) of Mn dust for 6 h/day, 5 days/wk for 13 consecutive weeks and compared to a control group of 12 rats (C) exposed to 4 microg/m(3). After exposure, neurological evaluation was carried out for 36 h (a night-day-night cycle) using a computerized autotrack system. Rats were then sacrificed by exsanguination, and Mn content in organs and tissues was determined by neutron activation analysis. Mn concentrations in lung, putamen, and cerebellum were significantly higher in E than in C (0.30 vs. 0.17, 0.89 vs. 0.44, 0.63 vs. 0.48 ppm; p <.01), as well as in the kidney, frontal cortex, and globus pallidus (1.15 vs. 0.96, 0.84 vs. 0.47, 1.28 vs. 0.55 ppm; p <.05). Potassium concentration was significantly lower in E than in C (5.11 vs. 5.79 mmol/L; p <.05), as was alkaline phosphatase (106.9 vs. 129.6 U/L; p <.01). Locomotor activity indicated higher distance covered in the first 12-h period for E (45 383 vs. 36 098 cm; p <.05) and lower resting time in the last 12-h period for E (36 326 vs. 37 393 s; p <.05). This study is the first of several ongoing studies in our laboratory that address health concerns associated with inhalation exposure to different Mn species and to different levels of exposure.

A Possible Neuroprotective Action of a Vinylic Telluride against Mn-Induced Neurotoxicity

“…Behavioral tests, such as the open-field task, permit the evaluation of primary motor activity. Previous studies have shown that Mn exposure can increase (St-Pierre et al, 2001), decrease (Vezer et al, 2007), or result in unchanged activity levels in animals, dependent upon the route of administration, the dose, and the exposure period (Dorman et al, 2000). The present study establishes decreased exploratory activities in Mn-treated rats in a chronic low-dose drinking water exposure paradigm.…”

Oxidative damage and neurodegeneration in manganese-induced neurotoxicity

“…Images of neurons with Neurolucida-assisted morphometry show that Mn-induced oxidative damage and neuroinflammation targeted the dendritic system with profound dendrite regression of striatal MSNs. When administered to adult rodents, excess Mn accumulates in various basal ganglia structures, including the striatum (caudate and putamen), globus pallidus, and brain stem (Autissier et al, 1982; Dorman et al, 2000; Calabresi et al, 2001; St-Pierre et al, 2001). The striatum is a major recipient structure of neuronal efferents in the basal ganglia.…”

Short-term manganese inhalation decreases brain dopamine transporter levels without disrupting motor skills in rats

“…Our results are different from other studies that reported Mn neurotoxicity. For example, welders exposed to Mn have demonstrated decreased motor function (Bowler et al, 2006;Ellingsen et al, 2008), and a previous Mn exposure study in rats also showed altered locomotor activity (Normandi et al, 2004;Tapin et al, 2006;St-Pierre et al, 2001). It is possible that in our study, the exposure duration may not have been long enough to induce structural brain damage and neurobehavioral changes, but sufficient to elicit altered expression of dopamine transporter.…”

“…This lack of exposuredependence in liver Mn levels has been observed in several studies of Mn inhalation in rats (Tapin et al, 2006;Yu et al, 2003;St-Pierre et al, 2001); this may be related to the short half-life of Mn in blood following short-term inhalation exposure (Smargiassi and Mutti, 1999).…”