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Effects of manganese exposure on dopamine and prolactin production in rat
Hyeon Yeong Kim1, Chae Kwan Lee, Jong Tae Lee
1Chemical Safety and Health Research Center, Occupational Safety and Health Research Institute, Yuseong-Gu, Daejeon, Korea.
Abstract:
Although manganese (Mn) has been shown to increase prolactin (PRL) by decreasing dopamine (DA) in the hypothalamus, the mechanism of Mn-induced regulation of the hypothalamic-hypophyseal-pituitary axis is unclear. We assessed the effects of inhaled Mn on hypothalamic DA and pituitary PRL production and evaluated the role of pituitary-specific transacting factor 1 (Pit-1), a transacting factor of PRL gene, in Mn-induced changes in PRL secretion in the rat brain. Male rats exposed to Mn for 4 or 13 weeks (1.5 mg/m3, 6 h/day, 5 days/week) showed a progressive and significant decrease in hypothalamic DA, whereas PRL and Pit-1 mRNA levels increased in response to Mn exposure. These results suggest that exposure to Mn decreases hypothalamic DA and promotes the production of PRL in the pituitary and that Pit-1 might be a regulator of DA and PRL.
Insights
Manganese (Mn) exposure in rats decreased hypothalamic dopamine (DA) and increased pituitary prolactin (PRL) and Pit-1 mRNA levels. This suggests Mn disrupts the hypothalamic-pituitary axis, potentially via Pit-1 regulation.
Area of Science:
- Neuroendocrinology
- Environmental Toxicology
- Molecular Biology
Background:
- Manganese (Mn) is known to increase prolactin (PRL) by decreasing hypothalamic dopamine (DA).
- The precise mechanism of Mn-induced regulation of the hypothalamic-hypophyseal-pituitary axis remains unclear.
- Pituitary-specific transacting factor 1 (Pit-1) is a key regulator of PRL gene expression.
Purpose of the Study:
- To investigate the effects of inhaled manganese on hypothalamic dopamine and pituitary prolactin production in rats.
- To evaluate the role of Pit-1 in manganese-induced alterations of prolactin secretion.
Main Methods:
- Male rats were exposed to inhaled manganese (1.5 mg/m3) for 4 or 13 weeks.
- Hypothalamic dopamine levels were measured.
- Pituitary prolactin and Pit-1 mRNA levels were assessed.
Main Results:
- Inhaled manganese exposure led to a progressive and significant decrease in hypothalamic dopamine levels.
- Prolactin and Pit-1 mRNA levels in the pituitary significantly increased following manganese exposure.
- A dose-dependent relationship was observed between manganese exposure duration and the observed changes.
Conclusions:
- Inhaled manganese exposure disrupts the hypothalamic-pituitary axis by decreasing hypothalamic dopamine.
- Manganese exposure promotes prolactin production in the pituitary, potentially mediated by Pit-1.
- Pit-1 may act as a regulator in the observed dopamine and prolactin level changes induced by manganese.
