Differential changes in rat brain nitric oxide synthase in vivo and in vitro by methylmercury

被引:38
作者
Shinyashiki, M
Kumagai, Y
Nakajima, H
Nagafune, J
Homma-Takeda, S
Sagai, M
Shimojo, N
机构
[1] Univ Tsukuba, Inst Community Med, Dept Environm Med, Tsukuba, Ibaraki 305, Japan
[2] Univ Tsukuba, Grad Sch Doctoral Program Med Sci, Tsukuba, Ibaraki 305, Japan
[3] Univ Tsukuba, Masters Program Environm Sci, Tsukuba, Ibaraki 305, Japan
[4] Natl Inst Environm Studies, Tsukuba, Ibaraki 305, Japan
关键词
nitric oxide synthase; enzyme activity; methylmercuric chloride; mercuric chloride; thiol compounds; inhibition;
D O I
10.1016/S0006-8993(98)00400-4
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Alterations in mRNA level, protein content and enzyme activity for nitric oxide synthase (NOS) in the cerebrum and cerebellum during a continuous exposure of neurotoxic metal, methylmercury, were examined in Wistar rats. Subcutaneous (s.c.) administration of methylmercuric chloride (MMC, 10 mg kg(-1) day(-1), 8 days) resulted in significant increases with time of NOS activities in the cerebrum (1.6-1.9-fold, 5-8 days) and cerebellum (1.4-fold, 8 days). RT-PCR and immunoblot analyses indicated that the increase in the enzyme activity caused by this metal appears to be due to increase in protein levels of neuronal NOS (iNOS), but not inducible NOS (iNOS) because little appreciable mRNA and protein for iNOS were seen during MMC exposure. The direct effect of mercuric compounds on nNOS activity in vitro was evaluated using 20,000 X g supernatant from rat cerebellum homogenate. In contrast to the in vivo observation, inorganic-, alkyl-, and aryl-mercuric compound showed potent inhibition of iNOS activity with IC50 values of 11-43 mu M, whereas dimethylmercury (DMM) was without effect on the enzyme activity. Further experiments indicated that the inhibition of iNOS by organomercurial occurred via thiol modification. (C) 1998 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:147 / 155
页数:9
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