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Changes in pituitary, hypothalamic and brain progestin-metabolizing enzyme activities during lactation
1Department of Biomolecular Chemistry, University of Wisconsin-Madison 53706.
Summary
Enzyme activities metabolizing progesterone change during rat lactation and weaning. These shifts in 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR) and 5 alpha-reductase impact neurosteroid levels, potentially affecting hormone release.
Area of Science:
- Neuroendocrinology
- Steroid Metabolism
- GABAergic Signaling
Background:
- Progesterone metabolism is crucial for neuroendocrine regulation.
- Lactation and weaning induce significant physiological changes.
- Specific enzyme activities influence neurosteroid synthesis and function.
Purpose of the Study:
- To investigate progesterone 5 alpha-reductase and 5 alpha-dihydroprogesterone 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR) activities in rat brain regions during lactation and weaning.
- To correlate changes in these enzyme activities with potential alterations in neurosteroid levels and their downstream effects.
Main Methods:
- Enzyme activity assays for progesterone 5 alpha-reductase and NADH/NADPH-linked 3 alpha-HSOR.
- Tissue analysis of anterior pituitary, hypothalamus, and brain from lactating (8 and 21 days postpartum) and non-lactating rats.
- Comparative analysis of enzyme levels across different physiological states.
Main Results:
- Pituitary 3 alpha-HSOR activities were significantly higher in early lactation (8 days postpartum) compared to weaning (21 days) or non-lactating states.
- Hypothalamic and brain progesterone 5 alpha-reductase activities were lower in lactating and weaning rats versus non-lactating controls.
- Brain NADH-linked 3 alpha-HSOR activity decreased at weaning.
- Hypothalamic NADPH-linked 3 alpha-HSOR increased at 8 days of lactation.
Conclusions:
- Tissue-specific changes in progesterone-metabolizing enzymes occur during lactation and weaning.
- These enzymatic shifts may alter the local production of neurosteroids like 3 alpha,5 alpha-tetrahydroprogesterone and 5 alpha-dihydroprogesterone.
- Modulated neurosteroid levels could influence GABAA receptor activity and the release of prolactin and gonadotropins.
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