Pulsatile release of oxytocin after suppression of prostaglandin synthesis in hysterectomised ewes.
On days 13 and 14 after oestrus (day 0) oxytocin and 13,14-dihydro-15-keto-prostaglandin (PG)F2 alpha (PGFM) concentrations were measured in jugular plasma of hysterectomised sheep with or without systemic treatment with the PG cyclo-oxygenase inhibitor indomethacin (4 mg kg-1 three times a day on days 12, 13 and 14 subcutaneously. Pulsatile increases of oxytocin were observed in both untreated and treated sheep with mean (+/- SD) peak heights of 18.4 +/- 9.6 pg ml-1 (n = 11) and 23.5 +/- 9.4 pg ml-1 (n = 8), respectively; these means were not significantly different. Plasma concentrations of PGFM remained consistently low in both groups (under 100 pg ml-1) with no significant peaks observed. The data suggest that PGF2 alpha may not be the only stimulus for the release of luteal oxytocin, or that there may be a contribution by the posterior pituitary to oxytocin secretion during the luteal phase of the ovine oestrous cycle.
Department of Veterinary Preclinical Sciences, University of Liverpool, Neston, South Wirral.
J H
JH
Payne
R G
RG
Cooke
D000204:Activity Cycles; D000818:Animals; D002940:Circadian Rhythm; D015237:Dinoprost / Q000097:blood / Q000378:metabolism*; D005260:Female; D007044:Hysterectomy / Q000662:veterinary*; D007213:Indomethacin / Q000494:pharmacology*; D010121:Oxytocin / Q000097:blood / Q000378:metabolism*; D012756:Sheep
D010121:Oxytocin; D015237:Dinoprost; D007213:Indomethacin