Increase in ovarian 15-hydroxyeicosatetraenoic acid during ovulation in the gonadotropin-primed immature rat.
The ovarian level of 15-hydroxyeicosatetraenoic acid (15-HETE) was measured by RIA during ovulation in gonadotropin-primed immature Wistar rats. The ovulatory process was initiated in 25-day-old rats by a 10-IU injection of hCG sc 2 days after the animals had been primed with 10 IU PMSG, sc. Ovarian follicles begin to ovulate 10 h after hCG. At 0 h after hCG, the ovarian 15-HETE level was 0.6 +/- 0.2 ng/mg ovarian protein. At 6 h the 15-HETE level increased sharply to 27.3 +/- 4.2 ng/mg protein and reached a peak of 50.0 +/- 9.8 ng/mg protein at 10 h. Ovarian 15-HETE decreased significantly between 10-16 h after hCG (when ovulation was essentially completed). The pattern of secretion of this 15-lipoxygenase product was reciprocal to the pattern of secretion of leukotriene-B4 by the rat ovary. Ovarian 15-HETE production and ovulation were inhibited in a dose-dependent manner when indomethacin was administered sc 1 h after hCG in doses ranging from 0.10-10.0 mg/rat. In contrast, the synthesis of ovarian prostaglandins-E and -F was inhibited by a dose of indomethacin as low as 0.0316 mg/rat, but this dose did not significantly affect the ovarian 15-HETE level or the ovulation rate. Therefore, the ovulation rate was more closely correlated with the ovarian 15-HETE level (P less than 0.001) than with the ovarian levels of either prostaglandin-E or -F (0.10 greater than P greater than 0.05). The results suggest that products of the 15-lipoxygenase pathway of arachidonic acid metabolism may be important in the biochemical events of mammalian ovulation.
Tanaka
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Department of Biology, Trinity University, San Antonio, Texas 78284.
Espey
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Okamura
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D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D005260:Female; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis*; D007213:Indomethacin / Q000494:pharmacology; D007700:Kinetics; D007975:Leukotriene B4 / Q000096:biosynthesis; D010053:Ovary / Q000187:drug effects / Q000502:physiology*; D010060:Ovulation / Q000187:drug effects; D011458:Prostaglandins E / Q000096:biosynthesis; D011460:Prostaglandins F / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation
D006063:Chorionic Gonadotropin; D006893:Hydroxyeicosatetraenoic Acids; D011458:Prostaglandins E; D011460:Prostaglandins F; D007975:Leukotriene B4; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D007213:Indomethacin