Effects of Sub-Acute Manganese Exposure on Thyroid Hormone and Glutamine (Gln)/Glutamate (Glu)-γ- Aminobutyric Acid (GABA) Cycle in Serum of Rats.

Excessive manganese (Mn) exposure may adversely affect the central nervous system, and cause an extrapyramidal disorder known as manganism. The glutamine (Gln)/glutamate (Glu)-γ-aminobutyric acid (GABA) cycle and thyroid hormone system may be involved in Mn-induced neurotoxicity. However, the effect of Mn on the Gln/Glu-GABA cycle in the serum has not been reported. Herein, the present study aimed to investigate the effects of sub-acute Mn exposure on the Gln/Glu-GABA cycle and thyroid hormones levels in the serum of rats, as well as their relationship. The results showed that sub-acute Mn exposure increased serum Mn levels with a correlation coefficient of 0.733. Furthermore, interruption of the Glu/Gln-GABA cycle in serum was found in Mn-exposed rats, as well as thyroid hormone disorder in the serum via increasing serum Glu levels, and decreasing serum Gln, GABA, triiodothyronine (T3) and thyroxine (T4) levels. Additionally, results of partial correlation showed that there was a close relationship between serum Mn levels and the detected indicators accompanied with a positive association between GABA and T3 levels, as well as Gln and T4 levels in the serum of Mn-exposed rats. Unexpectedly, there was no significant correlation between serum Glu and the serum T3 and T4 levels. In conclusion, the results demonstrated that both the Glu/Gln-GABA cycle and thyroid hormone system in the serum may play a potential role in Mn-induced neurotoxicity in rats. Thyroid hormone levels, T3 and T4, have a closer relationship with GABA and Gln levels, respectively, in the serum of rats.

[Application of multi-coeffieient of variation significance test for toxicology study].

OBJECTIVE: To establish the methods of calculating and analyzing the multi-coefficient of variation significance test for the toxicology study. METHODS: The paper aimed to confirm the significance level with the method of Bonferroni and then compared the methods of calculating and analyzing of the experiment groups with the control group respectively. RESULTS: The significance level of multi-coefficient of variation significance test was confirmed as alpha1=0.0167. Compared with the control groups, the activity of ALT in serum both in 30 mg/kg and 60 mg/kg groups did not change in the average significance test, which was not statistically significant (P>0.05), while it changed in the variation significance test, which was of statistical significance (P<0.0167). The activity of AST in serum in 60 mg/kg group did not change in the average significance test (P>0.05), while it changed in the variation significance test (P<0.0167). CONCLUSION: The complete changes of the indexes can only be shown by use of both the average significance test and the variation significance test together.