Interaction among beta-endorphin, nitric oxide and prostaglandins during ovulation in rats.
The aim of this study was to investigate the relationship between beta-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 beta-endorphin stimulated nitric oxide synthase (NOS) activity. This effect was completely reversed when naltrexone was co-injected with beta-endorphin. The stimulatory action of beta-endorphin on NOS activity was studied to determine whether it was exerted via prostaglandins. Treatment with prostaglandin E(2) (PGE(2)) completely reversed the beta-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 beta-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 beta-endorphin inhibited the expression of eNOS protein, whereas expression of iNOS protein was not detectable. Ovarian beta-endorphin content was diminished at 10 h after hCG injection. Treatment with prostaglandin synthesis inhibitors in vivo augmented the ovarian beta-endorphin content. In conclusion, these results indicate that beta-endorphin stimulates the activity of ovarian NOS indirectly by inhibiting prostaglandin production.
Faletti
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AG
Centro de Estudios Farmacológicos y Botánicos (CEFYBO), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Serrano 669, (1414), Buenos Aires, Argentina. aliciafaletti@ciudad.com.ar
Mohn
C
C
Farina
M
M
Lomniczi
A
A
Rettori
V
V
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D000077239:Meloxicam; D023421:Models, Animal; D009271:Naltrexone / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010053:Ovary / Q000737:chemistry / Q000378:metabolism*; D010060:Ovulation / Q000502:physiology*; D011448:Prostaglandin Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013843:Thiazines / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D001615:beta-Endorphin / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*
D006063:Chorionic Gonadotropin; D011448:Prostaglandin Antagonists; D013843:Thiazines; D013844:Thiazoles; D009569:Nitric Oxide; D009271:Naltrexone; D001615:beta-Endorphin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D015232:Dinoprostone; D000077239:Meloxicam; D007213:Indomethacin