Effect of finadyne on oestradiol-induced ovarian oxytocin and uterine PGF(2 alpha) secretory systems on day 15 after oestrus in ovarian autotransplanted ewes

This study was undertaken to determine whether induction of ovarian oxytoci n after oestradiol treatment on day 15 after oestrus is mediated through pr ostaglandin secretion by blocking prostaglandin synthesis using finadyne, a n inhibitor of the cyclo-oxygenase pathway. Nine ewes with ovarian autotran splants were assigned randomly to receive an i.m. injection of either oestr adiol benzoate (50 mug) in peanut oil (n = 5) or oestradiol benzoate plus f inadyne (2.2 mg kg(-1)) (n = 4) at 3 h intervals starting at the time of oe stradiol injection. Blood samples were collected from the ovarian and contr alateral jugular veins at 30 min intervals for 6 h before and at 15 min int ervals for up to 9 h after the oestradiol and finadyne injections. The secr etion rate of ovarian progesterone remained high in all ewes, thus indicati ng the presence of a functional corpus luteum. Peripheral oestradiol concen trations were significantly (P < 0.001) higher during the 9 h after oestrad iol injection in both groups. None of the oestradiol-finadyne-treated ewes showed significant pulses in either ovarian oxytocin secretion or release o f the prostaglandin F-2 alpha metabolite 13,14-dihydro-15-keto PGF(2 alpha) (PCFM) after injections. In ewes treated with oestradiol only, at least on e detectable pulse of ovarian oxytocin and jugular PCFM was observed with m ean +/- SEM amplitude of 17.7 +/- 7.29 ng min(-1) and 237.18 +/- 43.13 pg m l(-1), respectively. The areas under the curve for ovarian oxytocin and jug ular PGFM pulses were significantly increased after oestradiol treatment. T hese findings demonstrate that initiation of the arachidonic acid cascade i s important for the secretion of oxytocin after oestrogen treatment.