Manipulation of the periovulatory sex steroidal milieu affects endometrial but not luteal gene expression in early diestrus Nelore cows

In beef cattle, the ability to conceive has been associated positively with size of the preovulatory follicle (POF). Proestrus estradiol and subsequent progesterone concentrations can regulate the endometrium to affect receptivity and fertility. The aim of the present study was to verify the effect of the size of the POF on luteal and endometrial gene expression during subsequent early diestrus in beef cattle. Eighty-three multiparous, nonlactating, presynchronized Nelore cows received a progesterone-releasing device and estradiol benzoate on Day–10 (D−10). Animals received cloprostenol (large follicle-large CL group; LF-LCL; N = 42) or not (small follicle-small CL group; SF-SCL; N = 41) on D−10. Progesterone devices were withdrawn and cloprostenol administered 42 to 60 hours (LF-LCL) or 30 to 36 hours (SF-SCL) before GnRH treatment (D0). Tissues were collected at slaughter on D7. The LF-LCL group had larger (P < 0.0001) POF (13.24 ± 0.33 mm vs. 10.76 ± 0.29 mm), greater (P < 0.0007) estradiol concentrations on D0 (2.94 ± 0.28 pg/mL vs. 1.27 ± 0.20 pg/mL), and greater (P < 0.01) progesterone concentrations on D7 (3.71 ± 0.25 ng/mL vs. 2.62 ± 0.26 ng/mL) compared with the SF-SCL group. Luteal gene expression of vascular endothelial growth factor A, kinase insert domain receptor, fms-related tyrosine kinase 1, steroidogenic acute regulatory protein, cytochrome P450, family 11, subfamily A, polypeptide 1, and hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 7 was similar between groups. Endometrial gene expression of oxytocin receptor and peptidase inhibitor 3, skin-derived was reduced, and estrogen receptor alpha 2, aldo-keto reductase family 1, member C4, and lipoprotein lipase expression was increased in LF-LCL versus SF-SCL. Results support the hypothesis that the size of the POF alters the periovulatory endocrine milieu (i.e., proestrus estradiol and diestrus progesterone concentrations) and acts on the uterus to alter endometrial gene expression. It is proposed that the uterine environment and receptivity might also be modulated. Additionally, it is suggested that increased progesterone secretion of cows ovulating larger follicles is likely due to increased CL size rather than increased luteal expression of steroidogenic genes.     

Arginine vasotocin concentrations in the supraoptic nucleus of the lizard Anolis carolinensis are associated with reproductive state but not oviposition.

Arginine vasotocin (AVT) is a neuropeptide involved in reproductive function in many nonmammalian vertebrates. We determined brain and plasma AVT concentrations during the estrous cycle and oviposition in the lizard Anolis carolinensis. There were no differences in AVT concentrations in the plasma or any brain region during the ovipositional sequence. However, we found that females with an egg in each oviduct and a large pre-ovulatory follicle (diameter > 4.5 mm) in one-ovary had significantly higher AVT concentrations in the supraoptic nucleus (SON) of the hypothalamus than did females with small pre-ovulatory follicles in both ovaries. In a second study, females with an egg in each oviduct and a large pre-ovulatory follicle had significantly greater AVT concentrations in the SON than females with only one oviductal egg and a large pre-ovulatory follicle or females with an egg in each oviduct and a small pre-ovulatory follicle in each ovary. Concentrations of AVT in other brain regions and in the plasma did not differ among these groups. Changes in steroid profiles during estrous and/or direct neural communication between the uterus, ovary, and brain may account for the changes in AVT concentrations seen in the supraoptic nucleus during the estrous cycle of Anolis carolinensis.     

Phospholipid transfer protein (PLTP) mRNA expression is stimulated by developing embryos in the oviduct

In mammal, fertilization and early preimplantation embryo development occurs in the oviduct. Evidence is accumulating that the oviductal epithelia secrete various biomolecules to the lumen during the secretory phase of the estrus cycle to enhance embryo development. This secretory activity of the oviduct is under the regulation of steroid hormones. Observations also suggested that the gametes and embryos modulate the physiology and gene-expressing pattern of the oviduct. However, the underlying molecular changes remain elusive. We hypothesize that the developing embryos interact with the surrounding environment and affect the gene expression patterns of the oviduct, thereby modulating the oviductal secretory activity conducive to the preimplantation embryo development. To test this hypothesis, suppression subtractive hybridization (SSH) was used to compare the gene expressions in mouse oviduct containing transferred in vitro cultured preimplantation embryos with that of oviduct containing oocytes during the preimplantation period. We reported here the identification and characterization of phospholipids transfer protein (PLTP), which is highly expressed in the embryo-containing oviduct and localized at the oviductal epithelium by in situ hybridization. PLTP contains signal peptide putative for secretory function. More importantly, PLTP mRNA increases in the oviductal epithelia of pregnant, but not pseudo-pregnant mice when assayed by real-time PCR. Taken together, our data suggested that PLTP may play important role(s) during in vivo preimplantation embryo development. This molecule would be a target to delineate the mechanisms and the roles of oviductal secretory proteins on early embryonic development.     

Local distributions of oviductal estradiol, progesterone, prostaglandins, oxytocin and endothelin-1 in the cyclic cow

The cyclic patterns of hormones which regulate the activity of the oviduct in the cow have not been adequately reported. We studied progesterone (P4), estradiol 17 beta (E2), prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), oxytocin (OT) and endothelin-1 (ET-1) concentrations in the cow oviduct. Reproductive tracts from cyclic Holstein cows in the follicular phase (n = 5), post ovulation phase (n = 5) and luteal phase (n = 5) were collected at a slaughterhouse. Oviducts were separated from the uterus, the lumen vas washed with physiological saline, and the enveloping connective tissues were removed. The fimbria was then separated at first and then the rest was divided into 2 parts of equal length (proximal and distal). After extraction, levels of different hormones in the tissues were measured using double antibody enzyme immunoassays (EIAs). There were no differences in any hormone concentration between the 3 parts of the oviduct at any stage of the estrous cycle. The highest concentration of oviductal P4 was observed during the luteal phase and in the oviduct ipsilateral to the functioning CL. Oviductal OT was unchanged throughout the cycle. The highest E2 concentration was observed during the follicular phase in the oviduct ipsilateral to the dominant follicle. The oviduct ipsilateral to the dominant follicle during the follicular phase and ipsilateral to the ovulation site post ovulation showed higher levels of PGE2, PGF2 alpha and ET-1 than those on the contralateral side or during the luteal phase. The highest PGE2 was observed in the oviduct ipsilateral to the ovulation site during the post ovulation phase. The results suggest that the ovarian products (P4, OT and E2) and the local oviductal products (PGE2, PGF2 alpha, and ET-1) may synergistically control oviductal contraction for optimal embryo transport during the periovulatory period, and provide further evidence for the local delivery of ovarian steroids to the adjacent reproductive tract.     

Equine chorionic gonadotropin increases estradiol levels in the bovine oviduct and drives the transcription of genes related to fertilization in superstimulated cows

In the bovine oviduct, estradiol (E2) stimulates secretion and cell proliferation, whereas progesterone (P4) suppresses them. In this study, we have evaluated the effect of two superstimulatory protocols (follicle‐stimulating hormone [FSH] or FSH combined with equine chorionic gonadotropin [eCG]) on the oviductal levels of E2 and P4 and its outcome on oviductal cells. Compared with the control group (a single pre‐ovulatory follicle), we have observed that the cows submitted to FSH/eCG treatment showed a higher concentration of E2 in the oviduct tissue, together with a higher abundance of messenger RNA encoding steroid receptors (ESR1 and progesterone receptor), and genes linked to gamete interactions and regulation of polyspermy (oviduct‐specific glycoprotein 1, heat‐shock protein family A member 5, α‐l ‐fucosidase 1 [FUCA1], and FUCA2) in the infundibulum and ampulla segments of the oviduct. However, we did not observe any modulation of gene expression in the isthmus segment. Even though the FSH protocol upregulated some of the genes analyzed, we may infer that the steady effect of FSH combined with eCG on oviduct regulation might benefit fertilization and may potentially increase pregnancy rates.     

Vascular endothelial growth factor system in the cow oviduct: a possible involvement in the regulation of oviductal motility and embryo transport

Vascular endothelial growth factor (VEGF) is a potent angiogenic and permeability enhancing factor, which shows the highest activity in the oviduct during the periovulatory period of the estrous cycle in cattle. It has also been shown that the contraction activity of oviduct is highest during the periovulatory period. The present study therefore focused on the possible involvement of VEGF in the regulation of biosynthesis and secretion of contraction-relaxation-related substances in the cow oviduct. Possible autonomous VEGF system in the oviduct as well as its endocrine control was also studied. Bovine oviductal epithelial cells (BOEC) in the second passage were cultured with VEGF (1 ng/ml) alone or with luteinizing hormone (LH; 10 ng/ml), estradiol 17-beta (E2; 1 ng/ml), and/or progesterone (P4; 1 ng/ml). The levels of prostaglandins (PGs), endothelin-1 (ET-1), and angiotensin II (Ang II) in the medium were measured using second antibody enzymeimmunoassay (EIA). The mRNA expressions for cycloxygenase-2 (Cox-2), prostaglandin F synthase (PGFS), prostaglandin E synthase (PGES), prepro-ET-1, endothelin converting enzyme-1 (Ece-1), angiotensin converting enzyme-1 (Ace-1), VEGF and its receptors were investigated using real-time RT-PCR. The results indicate that, (1) VEGF dose-dependently stimulated the release of prostaglandin E2 (PGE2), prostaglandin F2alpha (PGF2alpha), and ET-1, but not Ang II. VEGF and VEGF with LH, E2, and P4 upregulated mRNA expression for biosynthesis cascade of PG, ET-1 as well as their release. However, only the combination of VEGF with LH, E2, and P4 upregulated mRNA for Ace-1 and Ang II release, but not VEGF alone. (2) Treatments of LH, with E2 and/or P4 increased the mRNA expression for VEGF, Flk-1 and Flt-1, and (3) VEGF itself downregulated the expression of mRNA for VEGF, and LH, E2, and P4 enhanced this downregulatory effect. The results of the present study provide the first evidence that (1) VEGF directly stimulates the biosynthesis and release of PGE2, PGF2alpha, and ET-1 in the bovine oviduct, (2) LH stimulates the oviductal VEGF system, and (3) VEGF downregulates the oviductal VEGF system and this downregulation was further intensified in the presence of LH. The data suggest that the preovulatory LH-surge, together with increasing E2 secretion from the Graffian follicle and basal P4 levels from the regressing corpus luteum (CL), upregulates the oviductal VEGF system, inducing the maximum oviductal production of contraction-relaxation-related substances for active oviduct contraction and rapid transport of gametes to the fertilization site. However, the oviductal VEGF elevation caused by the LH-surge, appears to downregulate the oviductal VEGF system immediately after ovulation thereby may contribute to suppress oviductal contraction to secure slow transport of the embryo to the uterus at the optimal time.     

Anandamide Levels Fluctuate in the Bovine Oviduct during the Oestrous Cycle

Mammalian oviduct acts as a reservoir for spermatozoa and provides an environment in which they may compete for the opportunity to fertilize the oocyte. Whilst in the oviduct spermatozoa undergo capacitation essential for fertilization. Sperm-oviduct interaction is essential for sperm capacitation and is a tightly regulated process influenced by the local microenvironment. Previously we reported that the endocannabinoid anandamide (AEA) regulates sperm release from epithelial oviductal cells by promoting sperm capacitation. The aims of this work were to measure the AEA content and to characterize the main AEA metabolic pathway in the bovine oviduct and determine how these change through the oestrous cycle. In this study, the levels of AEA and two other N-acylethanolamines, N-oleoylethanolamine and N-palmitoylethanolamine, were measured in bovine oviduct collected during different stages of oestrous cycle by ultra high performance liquid chromatography tandem mass spectrometry. Results indicated that intracellular oviductal epithelial levels of all three N-acylethanolamines fluctuate during oestrous cycle. Anandamide from oviductal fluid also varied during oestrous cycle, with the highest values detected during the periovulatory period. Endocannabinoid levels from ipsilateral oviduct to ovulation were higher than those detected in the contralateral one, suggesting that levels of oviductal AEA may be regulated by ovarian hormones. The expression and localization of N-acylethanolamines metabolizing enzymes in bovine oviduct were also determined by RT-PCR, Western blot, and immunohistochemistry but no change was found during the oestrous cycle. Furthermore, nanomolar levels of AEA were detected in follicular fluids, suggesting that during ovulation the mature follicle may contribute to oviductal AEA levels to create an endocannabinoid gradient conducive to the regulation of sperm function for successful fertilization.     

Regulation by Gonadal Steroids of Estrogen and Progesterone Receptors Along the Reproductive Tract in Female Lambs

The regulation of estrogen and progesterone receptor (ER, PR) expression by estradiol (E2) and progesterone (P4) in the oviduct, uterus and cervix of female lambs was studied. The animals received three intramuscular injections of E2, P4 or vehicle with an interval of 24 h and they were slaugthered 24 h after the third injection. Determinations of ER and PR were performed by binding assays and mRNAs of ERα and PR by solution hybridization. High levels of ER and PR in both cervix and oviduct were found in the female lamb, differing from other mammalian species. No significant effects by either E2 or P4 treatment on ER and PR levels in the cervix and oviduct could be observed. E2 treatment increased the mRNA levels of ERa and PR more than 3-fold in the cervix, while P4 treatment increased the mRNA levels of ERa and PR in the uterus. The results show differential effects of gonadal steroids on sex steroid receptor expression along the reproductive tract in female lambs, suggesting that steroid target tissues can modulate responses to the same circulating levels of steroid hormones.     

Endometriosis is associated with progesterone resistance in the baboon (Papio anubis) oviduct: evidence based on the localization of oviductal glycoprotein 1 (OVGP1)

Endometriosis has been associated with a reduced response to progesterone in both the eutopic and ectopic endometrium. In this study we evaluated OVGP1 and steroid receptor expression in oviducts of baboons with endometriosis during the midsecretory phase and determined whether progesterone resistance associated with endometriosis also occurs in the oviduct. Oviducts obtained during the window of uterine receptivity (Day 10 postovulation [PO]) from animals with induced and spontaneous disease were compared to control animals during the proliferative stage and in the implantation window as well as animals treated with the progesterone receptor (PGR) antagonist ZK 137.299 (ZK). OVGP1 was significantly higher in animals with endometriosis compared with Day 10 PO controls and was similar to that seen in the late proliferative phase and in ZK-treated animals. Baboons with spontaneous endometriosis also showed a similar persistence of OVGP1, which was correlated with the maintenance of estrogen receptor 1 (ESR1) in the epithelial cells of animals with endometriosis. However, epithelial cell height and the percentage of ciliation were not affected by endometriosis. These data imply that the normal antagonism of progesterone on ESR and OVGP1, which results in their downregulation during the window of implantation, is absent in animals with endometriosis. This was confirmed further when the action of PGR was antagonized in animals without disease, which also resulted in the persistence of ESR1 and OVGP1. These studies suggest that an aberrant oviductal environment may be an additive factor that contributes to endometriosis-associated infertility.     

Effects of interleukin-8 on estradiol and progesterone production by bovine granulosa cells from large follicles and progesterone production by luteinizing granulosa cells in culture

Interleukin 8 (IL-8) is a chemoattractant involved in the recruitment and activation of neutrophils and is associated with the ovulate process. We examined the possible role of IL-8 in steroid production by bovine granulosa cells before and after ovulation. The concentration of IL-8 in the follicular fluid of estrogen-active dominant (EAD) and pre-ovulatory follicles (POF) was higher than that of small follicles (SF). CXCR1 mRNA expression was higher in the granulosa cells of EAD and POF than that of SF. In contrast, CXCR2 mRNA expression was lower in granulosa cells of EAD and POF than in SF. IL-8 inhibited estradiol (E2) production in follicle-stimulating hormone (FSH)-treated granulosa cells at 48 h of culture. IL-8 also suppressed CYP19A1 mRNA expression in FSH-treated granulosa cells. IL-8 stimulated progesterone (P4) production in luteinizing hormone (LH)-treated granulosa cells at 48 h of culture. Although IL-8 did not alter the expression of genes associated with P4 production, it induced StAR protein expression in LH-treated granulosa cells. The expression of CXCR1 mRNA in corpus luteum (CL) did not change during the luteal phase. In contrast, the expression of CXCR2 mRNA in middle CL was significantly higher than in early and regression CL during the luteal phase. In luteinizing granulosa cells, an in vitro model of granulosa cell luteinization, CXCR2 mRNA expression was downregulated, whereas CXCR1 mRNA expression was unchanged. IL-8 also stimulated P4 production in luteinizing granulosa cells. These data provide evidence that IL-8 functions not only as a chemokine, but also act as a regulator of steroid synthesis in granulosa cells to promote luteinization after ovulation.     

Expression of superoxide dismutases in the bovine oviduct during the estrous cycle

The superoxide dismutases (SODs) are first-line enzymatic antioxidants that dismute superoxide anion (O(2)(-)) to produce hydrogen peroxide (H(2)O(2)). The primary objective was to characterize, by western blot analysis, the expression of two SODs, the cytosolic (Cu,ZnSOD or SOD1) and the mitochondrial (MnSOD or SOD2) forms in three sections of the oviduct, i.e. isthmus (I), ishtmic-ampullary junction (IA), and ampulla (A), during the estrous cycle. The Cu,ZnSOD and MnSOD proteins were mostly expressed in the ampulla (I相似文献   

Regulation of complement-3 protein expression in human and mouse oviducts

The human oviduct derived embryotrophic factor-3 (ETF-3) contains complement protein-3 (C3) and its derivates. Although C3 is not embryotrophic, it is converted into the embryotrophic derivative, iC3b in the presence of embryos and oviductal cells. The regulation of C3 production in the oviduct is not known. The objectives of this study were to investigate the effects of presence of preimplantation embryos and hormones on C3 expression in the oviducts in vitro and in vivo. The expression of C3 in the oviduct of pregnant mice was compared to that of pseudo-pregnant mice. The hormonal action on C3 expression was studied in the ovariectomized mouse oviducts and human oviductal epithelial (OE) cells. The results showed that the level of C3 mRNA in the mouse oviduct was high on Day 1 and Day 2, but decreased to a minimum on Day 4 of pregnancy, whereas that of pseudo-pregnancy remained relatively stable within the same period. The protein levels of C3 and iC3b specific fragments, alpha-115 and alpha-40, respectively in the mouse oviductal luminal fluid were highest on Day 3 of pregnancy, when the embryos were expected to be most sensitive to the embryotrophic activity of ETF-3. Estrogen elevated C3 expression in the ovariectomized mouse oviduct and the OE cells. Progesterone suppressed estrogen-induced C3 expression in the mouse oviduct, but had no effect on OE cells. In conclusion, the presence of embryo and steroid hormones regulate the synthesis and secretion of oviductal C3.     

The role of the oviduct and extracellular vesicles during early embryo development in bovine

The oviduct is an important reproductive structure that connects the ovary to the uterus and takes place to important events such as oocyte final maturation, fertilization and early embryonic development. Thus, gametes and embryo can be directly influenced by the oviductal microenvironment composed by epithelial cells such secretory and ciliated cells and oviductal fluid. The oviduct composition is anatomically dynamic and is under ovarian hormones control. The oviductal fluid provides protection, nourishment and transport to gametes and embryo and allows interaction to oviductal epithelial cells. All these functions together allows the oviduct to provides the ideal environment to the early reproductive events. Extracellular vesicles (EVs) are biological nanoparticles that mediates cell communication and are present at oviductal fluid and plays an important role in gametes/embryo - oviductal cells communication. This review will present the ability of the oviducts based on its dynamic and systemic changes during reproductive events, as well as the contribution of EVs in this process.     

Angiotensin II and atrial natriuretic peptide in the cow oviductal contraction in vitro: direct effect and local secretion of prostaglandins, endothelin-1, and angiotensin II

Angiotensin II (Ang II) and atrial natriuretic peptide (ANP) may be involved in local regulation of the oviductal contraction during the estrous cycle. Thus, the in vitro effects of Ang II and ANP on the secretion and contraction of bovine oviduct during the follicular, postovulatory, and luteal phases were investigated. An in vitro microdialysis system (MDS) was utilized to determine the intraluminal release of prostaglandins (PGs), Ang II, and endothelin-1 (ET-1) from the bovine oviducts as well as to observe the effect of Ang II and ANP on the local secretion of these substances. The basal release of PGs, ET-1, and Ang II was higher (P < 0.05) during the follicular and postovulatory phases than during the luteal phase. Stimulation by infusion of Ang II (10(-6) M) or ANP (10(-7) M) into the MDS was carried out for 4 h between 4 and 8 h of incubation. In the oviducts from the follicular and postovulatory phases, the infusion of ANP increased the release of Ang II, but not of ET-1. Infusion of Ang II stimulated the release of ET-1. Both Ang II and ANP increased PGE(2) and PGF(2alpha) release. In the contraction study, direct administration of Ang II (10(-7) M) or ANP (10(-8) M) into the medium during the follicular and postovulatory phases increased the amplitude of oviductal contraction. In contrast, these substances did not show any effect in the contraction and secretion of oviducts from cows during the midluteal phase. These results indicate that during the periovulatory period, Ang II and ANP stimulate the contractile amplitude of the oviduct in vitro. In addition to their direct action on oviductal contraction, Ang II may activate oviductal secretion of ET-1 and PGs. Likewise, ANP stimulates oviductal secretion of PGs and Ang II. Hence, the overall results suggest the existence of a functional endothelin-angiotensin-ANP system in the bovine oviduct during the periovulatory period, which may regulate the oviductal contraction to ensure maximum efficiency of gamete/embryo transport through the oviduct.     

Effects of stress upon plasma estradiol and progesterone levels and the rate of oviductal embryo transport in the rat.

The possibility that changes in sex steroid levels associated with stress could alter the rate of oviductal embryo transport was investigated in the rat. To this end, the effect of cold-swimming and cold-restraint upon estradiol (E2) and progesterone (P) serum levels and embryo transport were assessed. Swimming in water at 16 degrees C for 10 min two or four times between 16:00 and 22:00 h on day 3 of pregnancy caused a modest acceleration of embryo transport that was not associated with decreased fertility. Restraint at 10 degrees C for 2 h between 13:00 and 15:00 h on the first 4 days of pregnancy did not affect embryo transport. Both stimuli increased corticosterone serum levels. Cold-swimming produced a severe hypothermia as compared to cold-restraint and increased serum E2, decreasing significantly the ratio P/E2. Cold-restraint increased the P/E2 ratio. When rats swam in cold water for 10 min twice and were rewarmed by immersion in water at 38 degrees C during 20 min, embryo transport was accelerated despite that no changes occurred in the blood levels of sex steroids. It is concluded that oviductal embryo transport is minimally affected by stress in the rat and that the effect of acute immersion may be independent of alterations in circulating sex steroid levels.     

Oviductal cell proteome alterations during the reproductive cycle in pigs

The mammalian oviduct plays a crucial role in events leading to the establishment of pregnancy. During the reproductive cycle, the reproductive system undergoes various changes, including alterations in the number of different cell types in the oviductal epithelium and changes in the height of oviductal cells. Maintaining the unique oviductal environment required for the fertilization and early embryonic development comes with an energy cost to the organism. Therefore, it is hypothesized that structural and functional changes to the oviduct during the reproductive cycle represent vital preparations for the development of suitable environments for conception and embryo support. Here, we aimed to identify the changes in protein expression profile that occur during the follicular and luteal stages of the reproductive cycle in oviductal epithelial cells. The porcine oviductal epithelial cell proteomes from the follicular and luteal stages of the reproductive cycle were contrasted after separation by 2-D gel electrophoresis. Several oviductal epithelial cell proteins were up- or down-regulated during the reproductive cycle. We checked the quantitative changes of two of these molecules during different stages of the reproductive cycle using Western blot analysis. Finally, a number of these proteins were identified using tandem mass spectrometry. The results demonstrated distinctive differences in the proteomic profiles of the oviduct between follicular and luteal phases of the reproductive cycle.     

Prostaglandin E2, prostaglandin F2 alpha and endothelin-1 production by cow oviductal epithelial cell monolayers: effect of progesterone, estradiol 17 beta, oxytocin and luteinizing hormone

The optimal oviductal environment, including contractile activity for gamete transport, fertilization and early embryonic development, is mediated by physiological and anatomical changes in the oviduct during the estrous cycle. Oviductal epithelial cell culture was utilized to investigate the effect of ovarian steroids (progesterone [P4] and estradiol 17 beta [E2]), oxytocin (OT) and luteinizing hormone (LH) on the local production of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha) and endothelin-1 (ET-1) in the cow oviduct. Epithelial cells isolated from oviducts collected during the follicular phase were cultured in M199 under standard culture conditions until monolayer formation. Then the cells were trypsinized and plated at a density of 3 x 10(4)/mL/well and cultured again until subconfluency, at which time the cells were incubated for 4 or 24 h with M199 only (control), high P4 (H-P4; 1 microgram/mL), low P4 (L-P4; 10 ng/mL), E2 (1 ng/mL), LH (10 ng/mL), OT (10(-9) M) ET-1 (10(-9) M), PGE2 (10(-8) M) PGF2 alpha (10(-9) M) or their combination (H-P4 + E2, L-P4 + E2, LH + E2, ET-1 + E2, L-P4 + E2 + LH and H-P4 + E2 + LH). The production of both PG and ET-1 was increased by E2 + low P4 and LH + E2 + low P4 (P < 0.05), while LH + E2 enhanced the production of PGF2 alpha and ET-1 (P < 0.05). Moreover, E2 + ET-1 stimulated PG production (P < 0.05). However, OT had no effect on the production of any of these substances. These results suggest that the preovulatory LH surge, together with locally re-circulated high levels of E2 from the Graafian follicle and basal P4 from regressing corpus luteum (CL), induces the maximum stimulatory effect on oviductal PGE2, PGF2 alpha and ET-1 production during the periovulatory period. Consequently, the elevated local ET-1 concentration during periovulatory period may induce the high contractile activity of the oviduct and, at the same time, the stimulation of PG production. Thus, ET-1 may act as a local amplifier for oviductal PG production stimulated by LH and ovarian steroids.