Abstract
Sexual differences on thyroxine 5'-deiodinase (5'-D) in the Harderian gland of Syrian hamsters were investigated. We compared the 24-h profile of 5'-D activity in male and female hamsters, observing a clear rhythm in males but not in females. Female values were always significantly higher than male ones. After pinealectomy day/night variations in male 5'-D activity at the time points studied were abolished, results that are in correlation with serum thyroid hormones. We also studied the regulation by androgen of the enzyme activity. Basal 5'-D activity increased in castrated males and levels fell when animals were implanted with testosterone or its product 5α- dihydrotestosterone (DHT). Female 5'-D activity was also inhibited by androgens. As only the addition of DHT in the presence of epitestosterone, an inhibitor of the conversion of testosterone on DHT, in castrated males was able to decrease 5'-D activity to the control animal levels, we suggest a probable direct effect of DHT by itself.
Original language | English (US) |
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Pages (from-to) | 397-404 |
Number of pages | 8 |
Journal | Journal of Cellular Biochemistry |
Volume | 62 |
Issue number | 3 |
DOIs | |
State | Published - Sep 1 1996 |
Externally published | Yes |
Keywords
- 5'-deiodinase activity
- 5α- dihydrotestosterone
- Harderian gland
- Syrian hamster
- pinealectomy
- rhythm
- testosterone
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology