Abstract
The aim of this study was to investigate the relationship between β-endorphin and nitric oxide (NO) during the ovulatory process in rats. Immature rats were treated with equine chorionic gonadotrophin-hCG to induce ovulation. An intrabursal injection of β-endorphin stimulated nitric oxide synthase (NOS) activity. This effect was completely reversed when naltrexone was co-injected with β-endorphin. The stimulatory action of β-endorphin on NOS activity was studied to determine whether it was exerted via prostaglandins. Treatment with prostaglandin E2 (PGE2) completely reversed the β-endorphin-induced stimulation of NOS activity. Moreover, intrabursal injection of meloxicam, an inhibitor of cyclooxygenase 2, increased NOS activity, but this effect was not altered by co-injection with β-endorphin. The presence of both endothelial NOS (eNOS) and inducible NOS (iNOS) in the ovary at 10 h after hCG treatment was studied by western blot analysis. Local administration of β-endorphin inhibited the expression of eNOS protein, whereas expression of iNOS protein was not detectable. Ovarian β-endorphin content was diminished at 10 h after hCG injection. Treatment with prostaglandin synthesis inhibitors in vivo augmented the ovarian β-endorphin content. In conclusion, these results indicate that β-endorphin stimulates the activity of ovarian NOS indirectly by inhibiting prostaglandin production.
Original language | English (US) |
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Pages (from-to) | 469-477 |
Number of pages | 9 |
Journal | Reproduction |
Volume | 125 |
Issue number | 4 |
DOIs | |
State | Published - Apr 1 2003 |
Externally published | Yes |
ASJC Scopus subject areas
- Reproductive Medicine
- Embryology
- Endocrinology
- Obstetrics and Gynecology
- Cell Biology