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

Abstract

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 < 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 < 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 PGE 1 than PGE 2 or PGF 2α (P < 0.005). It was particulary interesting to find that after flushing the oviducts, tissue production of PGE 1, PGE 2 and PGF 2α was similar. Finally, when dose response curves for PGE 1 and for PGE 2 on the spontaneous contractions of oviducts isolated from rats at proestrus, estrus and metestrus were constructed, both PGs evoked an inhibitory inotropic action. The ED 50 for PGE 1 in tubes from estrous rats was significantly smaller (P < 0.01) than that for metestrous animals but significantly greater (P < 0.01) than that observed in oviducts from proestrous rats. The ED 50 for PGE 2 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.