Influence of ova within rat oviducts on spontaneous motility and on prostaglandin production.

The present study was performed in order to explore the influence of ova present within rat oviducts on: a) tubal spontaneous motility and b) oviduct prostaglandin production. It was found that the isometric developed tension (IDT) of tubes isolated from proestrous rats (preovulatory oviducts) was significantly higher (P less than 0.01) than the IDT of tubes from rats at estrus and at metestrus (postovulatory oviducts). After flushing the oviducts with KRB solution (i.e., after removing existing ova) the IDT of the oviducts obtained from estrous rats increased significantly (P less than 0.01), whereas the IDT of tubes isolated from proestrous rats (i.e., preparations without ova) was not modified. On the other hand, isolated tubes containing their corresponding ova released into the suspending solution significantly more PGE1 than PGE2 or PGF2 alpha (P less than 0.005). It was particularly interesting to find that after flushing the oviducts, tissue production of PGE1, PGE2 and PGF2 alpha was similar. Finally, when dose response curves for PGE1 and for PGE2 on the spontaneous contractions of oviducts isolated from rats at proestrus, estrus and metestrus were constructed, both PGs evoked an inhibitory inotropic action. The ED50 for PGE1 in tubes from estrous rats was significantly smaller (P less than 0.01) than that for metestrous animals but significantly greater (P less than 0.01) than that observed in oviducts from proestrous rats. The ED50 for PGE2 did not change in the different tested periods of the sex cycle. Results reported herein suggest the possibility that the ova present within rat oviducts, may influence their own transport along the tubes by modifying the amount of prostaglandins produced by the oviducts or via their own prostaglandin synthesis.

The involvement of oxytocin in ovulation and in the outputs of cyclo-oxygenase and 5-lipoxygenase products from isolated rat ovaries.

The effects on ovulation of a specific anti-oxytocin rabbit serum (anti-OT) (50.0 microliters) given by intrabursal injection into the right ovaries of etherized adult female rats at proestrus, were explored by counting the number of ovulated ova present within the right oviducts. Left ovaries were not treated and served as control ovaries. Control rats were treated with male normal rabbit serum (NRS) (50.0 microliters) given by intrabursal injections into the right ovaries of animals at proestrus. Ovulation was induced by injection of human chorionic gonadotrophin (hCG). Anti-OT administered into the right ovarian bursae of proestrous rat ovaries evoked a significant 51% inhibition of ovulation in comparison with that observed in control non-injected left ovaries (p less than 0.01). Also, when the ovulation of right ovaries injected with anti-OT was compared with that of left ovaries injected with NRS, the number of ovulated ova in the right side was significantly smaller (30%) than on the contralateral side (p less than 0.02). However, in rats pre-treated with hCG the intrabursal injection of oxytocin (OT) (50.0 mU/ml) into right and left ovaries failed to alter the number of ovulated ova compared with that of rats receiving intrabursal injections of saline. The basal control and the OT-evoked synthesis and release of endogenous prostaglandin E2 (PGE2) and PGF2 alpha were explored in ovaries isolated from prepuberal rats injected with pregnant mare's serum gonadotrophin (PMSG), two days prior to sacrifice. OT augmented the basal release of PGF2 alpha but did not influence that of PGE2. Moreover, the conversion of exogenous 14C-arachidonic acid (14C-AA) into different prostanoids and into 5-HETE, in the presence and in the absence of added OT (50.0 mU/ml), was studied in rat ovaries isolated in proestrus. The challenge with OT augmented the basal synthesis and release of PGF2 alpha and of 5-HETE from 14C-AA, but failed to influence the formation of products generated via the cyclo-oxygenase pathway, namely 6-keto-PGF1 alpha, PGE2 and thromboxane B2 (TXB2). Therefore, the present results suggest that ovarian OT may play a role in the ovulatory process, via generation of PGF2 alpha to enhance contractions of ovarian smooth muscle and of 5-HETE to promote follicular collagenolysis.