Annals of Occupational and Environmental Medicine

Effect of Developmental Lead Exposure on the Expression of Hippocampal NMDA Receptor Subunit mRNA: Tae Wan Kim, In Sung Chung, Jae Hoon Bae, Dong Hoon Shin, Mi Young Lee, Joon Sik Kim; Korean Journal of Occupational and Environmental Medicine 2005;17(4):278-287. Published online December 31, 2005; DOI: https://doi.org/10.35371/kjoem.2005.17.4.278

Abstract PDF: OBJECTIVES
The purpose of the present study was to examine the differential effects of lead (Pb) exposure on the expression of specific NMDA receptor subunit mRNAs on the hippocampal cells depending on the neuronal developmental stage.
METHODS
Expression of the NR2A and NR2B subunits of the NMDA receptors mRNA on the hippocampal neurons was measured by in situ hybridization in the control and Pb treated groups. Pb-treated and NMDA cytotoxicity was assessed by morphological examination and LDH measurements.
RESULTS
Hippocampal NR2A subunit mRNA expression was gradually increased with increasing age, and was significantly decreased after Pb exposure. The expression of NR2B subunit mRNA was not changed during development in the rat hippocampus and the developmental effect of Pb exposure on NR2B expression was minimal. These results indicate that chronic Pb exposure may decrease the levels of NR2A-containing NMDA receptors and may thereby alter normal synaptic signal transmission. Pb or NMDA-induced cytotoxicity in vitro differed significantly between the immature and the mature hippocampal cells.
CONCLUSIONS
This study demonstrates that chronic Pb exposure during brain development alters the levels of specific NMDA receptor subunit mRNA in the rat hippocampus. These results suggest that chronic Pb exposure may attenuate the precise neuronal synaptic transmission through the differential alteration of the composition of the NMDA receptor subunit on the hippocampus depending on neuronal developmental stage.

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Plasma Malondialdehyde, alpha-tocopherol and Erythrocyte Superoxide Dismutase Activity with Blood Level of Heavy Metals in Welders: Won Jin Lee, Cheon Hyun Hwang, Soung Hoon Chang, Byung Chul Chun, Hae Joon Kim; Korean Journal of Occupational and Environmental Medicine 1998;10(2):240-250. Published online May 31, 1998; DOI: https://doi.org/10.35371/kjoem.1998.10.2.240

Abstract PDF: We investigated the association between the oxidative stress and the concentration of heavy metals in blood among welders. The study subjects were male manual CO2 welders(N=127) exposed to several heavy metals. The age distribution was from 20 to 63 (GM=33.7) and the geometric mean(GM) of work duration was 4.2 years. We analyze the level of blood lead, cadmium, managese and chromium which was related with the oxidative stress in the animal studies. Blood selenuim, plasma malondialdehyde (MDA), plasma alpha-tocopheol and orythrocyte superoxide dismutase (SOD) were analyzed as biological markers of the oxidative stress. The results of univariate analysis showed that the plasma MDA was significantly correlated with D-tocopherol (r=0.327) and blood selenium (r=0.313) concentration. But we could not find out any relationship between the erythrocyte SOD activities and those metal concentrations. Neither smoking nor alcohol consumption was related to the level of heavy metals and the oxidative stress biomarkers. As the results of multiple regression analysis with stepwise selection method, 1) the change of MDA level were dependant with the level of alpha-tocopherol and blood selenium concentration (R2=19.7), 2) the plasma alpha-tocopherol level was dependant with MDA and blood chromium concentration (R2=15.6), 3) in case of erythrocyte SOD activity, only the duration of work was significantly selected.

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Protective Effects of the NMDA-receptor Antagonist (MK-801) for the Brain Injury by Oxygen Free Radical: In the Hyperbaric Oxygen Treatment of CO Poisoned Rat: Dae Eun Jung, Seung Ho Ryu, Jin A Cho, Jae Cheol Song, Hung Bae Park; Korean Journal of Occupational and Environmental Medicine 1997;9(1):40-48. Published online February 28, 1997; DOI: https://doi.org/10.35371/kjoem.1997.9.1.40

Abstract PDF: The effects of NMDA-receptor antagonist (MK-801) were assessed for the oxygen free radical mediated brain (hippocampus) injury with eighty rats which were exposed to carbon monoxide (CO) followed by hyperbaric oxygen (HBO) treatment. Superoxide dismutase (SOD) and malondialdehyde (MDA) were used as parameters of the oxygen free radical reaction. Experimental groups consisted of (1) control group (=breathing with air), (2) CO group (=exposed to CO after air breath), (3) CO-air group(exposed to CO after air breath followed by air breath), and (4) CO-HBO group (=exposed to CO after air breath followed by 3 ATA HBO). Each group was divided two subgroup according to the pretreatment (normal saline or MK-801). CO, CO-air and HBO groups increased in SOD activity as compared with control group. And CO-air and HBO groups increased in MDA as compared with control and CO group. Pretreatment of MK-801 decreased SOD activities significantly (p-value<.05) , but MDA amount not significantly (p-value=.107). These results suggest a useful protective effect of NMDA-receptor antagonist (MK-801) in CO induced hippocampal injury mediated by oxygen free radicals.

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