Effect of subchronic treatment with mercury chloride on NTPDase, 5′-nucleotidase and acetylcholinesterase from cerebral cortex of rats

The aim of the present investigation was to evaluate the effect of a subchronic treatment (30 days/30 doses) with subcutaneous injections (0.1 mg/kg) of HgCl₂ on NTPDase (E.C. 3.6.1.5), 5′-nucleotidase (E.C. 3.1.3.5) and acetylcholinesterase (AChE, E.C. 3.1.1.7) activities in brain from adult rats. NTPDase and 5′-nucleotidase were measured in cortical synaptosomal fraction and AChE was measured in the homogenate of cerebral cortex and hippocampus. After the subchronic treatment (30 days), NTPDase activity was enhanced approximately 35% (p < 0.05) with ATP and ADP as substrates and no difference was observed in 5′-nucleotidase activity (AMP hydrolysis). In addition, AChE activity was enhanced in the cerebral cortex (22%, p < 0.05) and hippocampus (26%, p < 0.05) after the subchronic treatment. Mercury deposited in brain was measured by cold vapor (atomic absorption spectrometry) and no difference between the control and the subchronically treated group was observed. Here we showed for the first time that exposure to low levels of Hg²⁺, which resembles occupational exposure to low levels of mercury, caused a marked increase in NTPDase and AChE activities. The relationship of these alterations with the neurotoxicity of inorganic mercury deserves further studies.