Distribution of progesterone in the uterus, broad ligament, and uterine arteries of beef cows

Morphologic, Steroidogenic, and Transcriptomic Assessment of the Corpus Luteum in Holstein Cows after Spontaneous or Hormone-Induced Ovulation

There is evidence that replacing the gonadotropin-releasing hormone (GnRH) with porcine luteinizing hormone (pLH) to synchronize ovulation prior to artificial insemination (AI) increased pregnancy per AI in dairy cows without affecting blood progesterone (P₄) concentrations. Whether morphologic, steroidogenic, and transcriptomic differences exist among corpora lutea (CL) formed after ovulation induced by GnRH and pLH is unclear. Our main objective, therefore, was to compare CL characteristics between GnRH- and pLH-induced CL. In 24 non-lactating Holstein cows, ovulations were spontaneous (Spont-Ov) or induced with 100 µg GnRH, 25 mg pLH, or 1 mg estradiol benzoate (EB), with CL excised 12 d after ovulation. In pLH- versus GnRH-treated cows, the duration of elevated LH (above baseline) was prolonged (10 versus 6 h, respectively, p < 0.01), but CL dimensions, pixel intensity of CL images, proportions of steroidogenic and non-steroidogenic luteal cells, and mean plasma LH did not significantly differ. Post-ovulation mean plasma P₄ (ng/mL) did not differ among Spont-Ov (3.0) pLH (3.1) or GnRH (3.0) cows but were lower in EB cows (2.0). In vitro P₄ concentration was greater in luteal explants of pLH-treated cows than in all other groups (combined means, 16.0 vs. 12.3 µg/mL, p < 0.02). Relative abundance of mRNA for oxytocin receptor (OXTR) was 2-fold higher (p < 0.01) in CL of pLH vs. GnRH cows and highest in Spont-Ov CL. In summary, pLH-treated cows had a longer LH peak, and greatest luteal tissue concentrations and in vitro production of P₄. We inferred that increased P₄ concentrations at the ovarian-uterine level in pLH-treated cows could have promoted embryo development and increased pregnancy per AI.

Endometrial gene expression in response to lipopolysaccharide between estrous cycle phases and uterine horns in cattle

Uterine bacterial community abundances shift throughout the estrous cycle, potentially altering the immunological environment of the uterus and impacting subsequent fertility. The objective of the current study was to evaluate the immunological impact of lipopolysaccharide (LPS), as a model for potentially pathogenic bacteria, throughout the uterine endometrium between the luteal and follicular phase of the estrous cycle. Bovine uterine tracts were harvested in mid-luteal (n = 7) or follicular (n = 7) phase. Explants were collected from the contralateral and ipsilateral horn relative to the dominant follicle or corpus luteum, then subjected to one of three treatments: uncultured control, cultured control, or cultured with LPS (1 µg/mL). Explants underwent RNA extraction and targeted RNA sequencing for expression analyses of 40 immune response related genes. Sequencing reads were mapped to Bos taurus genome in CLC Genomics Workbench. Resulting total read counts were normalized by housekeeping gene GAPDH and analyzed for overall expression profile by Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) and Variable Importance in Projection (VIP) analyses in Metaboanalyst. Individual gene expression differences were determined by GLIMMIX procedure in SAS with fixed effects of treatment, estrous phase, uterine horn, and their interaction, with random effect of individual uterus. Expression of 29 genes were affected among treatment groups, with seven genes increased in LPS treatment compared to other groups (P &lt; 0.05). Multiple genes were affected by estrous phase and uterine horn, independent of treatment (P &lt; 0.05). The OPLS-DA analyses indicated overall gene expression differences due to clustering by estrous cycle and treatment (P &lt; 0.001), with no effect of uterine horn (P &gt; 0.10). Similar clustering was observed between luteal and follicular phase explants of controls, but distinct separate clustering between phases with LPS treatment (P = 0.001). According to VIP analyses, mucins were identified as contributing the most to differences observed between phase and treatment. In conclusion, estrous cycle phase resulted in differing overall endometrial gene expression profiles of immune response to LPS treatment. Therefore, altered immunological environment of the uterus in response to bacteria at different estrous cycle stages may lead to differences in reproductive success.

Chemotactic behavior of Campylobacter fetus subspecies towards cervical mucus, bovine placenta and selected substances and ion

The chemotaxis of C. fetus subsp. venerealis and C. fetus subsp. fetus was determined in the presence of bovine cervical mucus and bovine placental extract. Some reported substances and ion in those materials, such amino acids, ferrous iron, hormones, sugars and organic acids were also investigated. Bovine cervical mucus, bovine placenta extracts and some substances and ion of these materials namely L–fucose, L– aspartate, L–glutamate, L–serine, ferrous iron, fumarate, pyruvate and succinate were chemoattractants. The chemottraction was significantly larger in higher concentrations of the tested substances and ion and significant differences among tested strains were also observed. Meso-erythritol and hormones bovine placental lactogen, 17β-estradiol, and progesterone did not elicit chemotactical response. In conclusion, this chemotactic behavior may guide the C. fetus navigation in the bovine host's genital tract and be an important cofactor of tissue tropism for this bacterium.

Symposium review: Progesterone effects on early embryo development in cattle

The causes of low fertility in dairy cattle are complex and multifactorial and may be due to compromised follicle development affecting oocyte quality, a suboptimal reproductive tract environment incapable of supporting normal embryo development, or a combination of both. Progesterone (P4) plays a key role in reproductive events associated with establishment and maintenance of pregnancy, through its effects on oocyte quality and its action on the uterine endometrium. Reduced P4 concentrations during growth of the ovulatory follicle are associated with lower fertility, and low concentrations of circulating P4 after ovulation have been associated with reductions in conceptus growth and elongation, decreased interferon-τ (IFNT) production, and lower pregnancy rates in cattle. In contrast, elevated concentrations of circulating P4 in the period immediately following conception have been associated with advancement of conceptus elongation, increased IFNT production, and, in some cases, higher pregnancy rates in cattle. Despite the potential beneficial effects of exogenous P4 supplementation on fertility, results of supplementation studies have been inconsistent. As part of the 2019 ADSA Reproduction Symposium, focusing on the etiology of pregnancy losses in dairy cattle, the aim of this review is to highlight recent findings from our group and others in relation to embryo-maternal interaction during bovine pregnancy establishment and the role of P4 in uterine biology and embryo development.

Intraovarian influence of bovine corpus luteum on oocyte morphometry and developmental competence, embryo production and cryotolerance

Three experiments were conducted to determine influence of the bovine corpus luteum (CL) on morphometric and functional characteristics of oocytes, and subsequent embryonic development. Cumulus-oocyte complexes were aspirated from two types of cows: 1) with a CL in one ovary (CL+) and without a CL in the contralateral ovary (CL-), 2) and from cows without CL in either ovary (C). Intracellular activity of the enzyme glucose-6-phosphate dehydrogenase (G6PDH), oocyte diameter and thickness of the zona pellucida were determined (Experiment 1). Then, the rate of in vitro oocyte maturation for each ovarian category was evaluated and oocyte diameter and zona pellucida thickness were measured after maturation (Experiment 2). In Experiment 3, in vitro embryo production and cryotolerance were assessed. The oocyte diameter was greater (P < 0.01) and the zona pellucida was thinner in CL+ than in CL- (P > 0.05) or C (P = 0.0131) ovaries. Activity of G6PDH was lower in oocytes from CL+ than CL- (P < 0.01) and C (P = 0.0148) ovaries. Rate of oocyte maturation, oocyte diameter and thickness of the zona pellucida after maturation did not differ among groups. Rate of cleavage was greater in zygotes from CL+ than from CL- or C (P < 0.01); and CL+ ovaries produced more total embryos on day 7 (P < 0.05) and more blastocysts (P < 0.01) than CL- and C ovaries. Rate of expansion and hatching of day-7 vitrified-warmed blastocysts at 24 and 48 h of culture did not differ among groups. In conclusion, oocytes collected from CL+ ovaries were larger and metabolically more prepared to continue maturation than those from ovaries lacking a CL. Also, rates of cleavage and yield of blastocysts were greater for oocytes from CL+ ovaries than from CL- and C ovaries. These findings indicate that a CL influenced oocyte developmental competence and embryonic development, presumably through intraovarian interactions.

Do differences in the endometrial transcriptome between uterine horns ipsilateral and contralateral to the corpus luteum influence conceptus growth to day 14 in cattle?

Embryo transfer to the uterine horn contralateral to the ovary containing the corpus luteum (CL) negatively impacts pregnancy establishment in cattle. Our aim was to compare the transcriptome and ability of the ipsilateral and contralateral uterine horns to support preimplantation conceptus survival and growth to day 14. In experiment 1, endometrial samples from both horns were collected from synchronized heifers slaughtered on day 5, 7, 13, or 16 post-estrus (n = 5 per time) and subjected to RNA sequencing. In experiment 2, 10 day 7 in vitro produced blastocysts were transferred into the uterine horn ipsilateral (n = 9) or contralateral to the CL (n = 8) or into both horns (i.e., bilateral, n = 9) of synchronized recipient heifers. Reproductive tracts were recovered at slaughter on day 14, and the number and dimensions of recovered conceptuses were recorded for each horn. A total of 217, 54, 14, and 18 differentially expressed genes (>2-fold change, FDR P < 0.05) were detected between ipsilateral and contralateral horns on days 5, 7, 13, and 16, respectively, with signaling pathways regulating pluripotency of stem cells, ErbB signaling pathway, and mTOR signaling pathway amongst the top canonical pathways. Site of embryo transfer did not affect recovery rate (48.0%, 168/350) or length of conceptuses (mean ± SE 2.85 ± 0.27 mm). Although differences in gene expression exist between the endometrium of uterine horns ipsilateral and contralateral to the CL in cattle, they do not impact conceptus survival or length between day 7 and 14.

Challenges in studying preimplantation embryo-maternal interaction in cattle

A comprehensive understanding of the complex embryo-maternal interactions during the preimplantation period requires the analysis of the very early stages of pregnancy encompassing early embryonic development, maternal recognition and the events leading to implantation. Despite the fact that embryo development until blastocyst stage is somewhat autonomous (i.e., does not require contact with the maternal reproductive tract and can be successfully recapitulated in vitro), many studies on ruminant embryo production have focused on the fundamental question of why: (i) only 30%-40% of immature oocytes develop to the blastocyst stage and (ii) the quality of such blastocysts continually lags behind that of blastocysts produced in vivo. Clear evidence indicates that in vitro culture conditions are far from optimal with deficiencies being manifested in short- and long-term effects on the embryo. Thus, enhanced knowledge of mechanisms controlling embryo-maternal interactions would allow the design of novel strategies to improve in vitro embryo conditions and reproductive outcomes in cattle.

Effect of chronic administration of a gonadotropin-releasing agonist on luteal function and pregnancy rates in dairy cattle

Increased embryonic losses may be associated with inadequate progesterone (P4) concentrations in high-producing lactating dairy cattle. The objectives of the present studies were to determine if chronic administration of a gonadotropin-releasing hormone (GnRH) agonist, Deslorelin, would increase circulating P4 concentrations and subsequently increase pregnancy rates in dairy cattle. Administration of Deslorelin for 12 days increased (p < .05) luteal volume and circulating P4 concentrations in primiparous lactating dairy cows, but increased only luteal volumes in multiparous cows. Treatment with Deslorelin increased Day 45 pregnancy rates in cows as compared to untreated controls. Chronic treatment with Deslorelin in dairy cattle; (a) increased luteal volume of the primary CL, (b) induced accessory CL, (c) increased circulating P4 concentration in primiparous cows only, (d) did not lengthen the estrous cycle upon removal of treatment, and (e) increased pregnancy rates. Although luteal volume was increased in multiparous cows and circulating P4 concentrations were not with Deslorelin treatment, there was an apparent effect on pregnancy rates. This hormonal strategy may represent a suitable model to address local effects of P4 and GnRH/luteinizing hormone on uterine environment and subsequent embryonic survival.

Pre-hatching embryo-dependent and -independent programming of endometrial function in cattle

The bovine pre-implantation embryo secretes bioactive molecules from early development stages, but effects on endometrial function are reported to start only after elongation. Here, we interrogated spatially defined regions of the endometrium transcriptome for responses to a day 7 embryo in vivo. We hypothesize that exposure to an embryo changes the abundance of specific transcripts in the cranial region of the pregnant uterine horn. Endometrium was collected from the uterotubal junction (UTJ), anterior (IA), medial (IM) and posterior (IP) regions of the uterine horn ipsilateral to the CL 7 days after estrus from sham-inseminated (Con) or artificially inseminated, confirmed pregnant (Preg) cows. Abundance of 86 transcripts was evaluated by qPCR using a microfluidic platform. Abundance of 12 transcripts was modulated in the Preg endometrium, including classical interferon-stimulated genes (ISG15, MX1, MX2 and OAS1Y), prostaglandin biosynthesis genes (PTGES, HPGD and AKR1C4), water channel (AQP4) and a solute transporter (SLC1A4) and this was in the UTJ and IA mainly. Additionally, for 71 transcripts, abundance varied according to region of the reproductive tract. Regulation included downregulation of genes associated with proliferation (IGF1, IGF2, IGF1R and IGF2R) and extracellular matrix remodeling (MMP14, MMP19 and MMP2) and upregulation of anti-adhesive genes (MUC1) in the cranial regions of uterine horn. Physical proximity to the embryo provides paracrine regulation of endometrial function. Embryo-independent regulation of the endometrial transcriptome may support subsequent stages of embryo development, such as elongation and implantation. We speculate that successful early embryo-dependent and -independent programming fine-tune endometrial functions that are important for maintenance of pregnancy in cattle.

Differential gene expression profiling of endometrium during the mid-luteal phase of the estrous cycle between a repeat breeder (RB) and non-RB cows

BACKGROUND

Repeat breeding directly affects reproductive efficiency in cattle due to an increase in services per conception and calving interval. This study aimed to investigate whether changes in endometrial gene expression profile are involved in repeat breeding in cows. Differential gene expression profiles of the endometrium were investigated during the mid-luteal phase of the estrous cycle between repeat breeder (RB) and non-RB cows using microarray analysis.

METHODS

The caruncular (CAR) and intercaruncular (ICAR) endometrium of both ipsilateral and contralateral uterine horns to the corpus luteum were collected from RB (inseminated at least three times but not pregnant) and non-RB cows on Day 15 of the estrous cycle (4 cows/group). Global gene expression profiles of these endometrial samples were analyzed with a 15 K custom-made oligo-microarray for cattle. Immunohistochemistry was performed to investigate the cellular localization of proteins of three identified transcripts in the endometrium.

RESULTS

Microarray analysis revealed that 405 and 397 genes were differentially expressed in the CAR and ICAR of the ipsilateral uterine horn of RB, respectively when compared with non-RB cows. In the contralateral uterine horn, 443 and 257 differentially expressed genes were identified in the CAR and ICAR of RB, respectively when compared with non-RB cows. Gene ontology analysis revealed that genes involved in development and morphogenesis were mainly up-regulated in the CAR of RB cows. In the ICAR of both the ipsilateral and contralateral uterine horns, genes related to the metabolic process were predominantly enriched in the RB cows when compared with non-RB cows. In the analysis of the whole uterus (combining the data above four endometrial compartments), RB cows showed up-regulation of 37 genes including PRSS2, GSTA3 and PIPOX and down-regulation of 39 genes including CHGA, KRT35 and THBS4 when compared with non-RB cows. Immunohistochemistry revealed that CHGA, GSTA3 and PRSS2 proteins were localized in luminal and glandular epithelial cells and stroma of the endometrium.

CONCLUSION

The present study showed that endometrial gene expression profiles are different between RB and non-RB cows. The identified candidate endometrial genes and functions in each endometrial compartment may contribute to bovine reproductive performance.

Steroid hormones in bovine oviductal fluid during the estrous cycle

Ovarian steroid hormones are major regulators of the physiology of the oviduct and reproductive events occurring within the oviduct. To establish a whole steroid profiling of the bovine oviductal fluid (OF) during the estrous cycle, contralateral and ipsilateral (to the corpus luteum or preovulatory follicle) oviducts were classified into four stages of the estrous cycle (n = 18-27 cows per stage): postovulatory (Post-ov), mid-luteal (Mid-lut), late luteal (Late-lut), and preovulatory on the basis of the ovarian morphology and intrafollicular steroid concentrations. Steroids were extracted from pools of 150 to 200 μL OF (three to 10 cows per pool; three to four pools per "stage × side" group), purified, fractioned by high-performance liquid chromatography, and analyzed by gas chromatography coupled with tandem mass spectrometry. The concentrations of progesterone (P4) in ipsilateral OF increased from Post-ov (56.9 ± 13.4 ng/mL) to Mid-lut (120.3 ± 34.3 ng/mL), then decreased from Late-lut (76.7 ± 1.8 ng/mL) to Pre-ov (6.3 ± 1.7 ng/mL), and were four to 16 times higher than in contralateral OF. Most P4 metabolites followed similar patterns of variation. Concentrations of 17beta-estradiol (E2) were significantly higher at Pre-ov (290.5 ± 63.2 pg/mL) compared with all other stages (<118.3 pg/mL), with no difference regarding the side of ovulation. Concentrations of androstenedione displayed a pattern similar to that of E2, whereas other androgens, estrone, and corticoids did not vary between stages or sides. In conclusion, a highly concentrated and fluctuating hormonal environment was evidenced in the bovine OF. These results could be useful to improve media for IVF, embryo development, and culture of oviductal cells.

Steroids in the equine oviduct: synthesis, local concentrations and receptor expression

Steroids play an important role in mammalian reproduction and early pregnancy. Although systemic changes in steroid concentrations have been well documented, it is not clear how these correlate with local steroid concentrations in the genital tract. We hypothesised that, in the horse, the preimplantation embryo may be subjected to high local steroid concentrations for several days. Therefore, we measured progesterone, 17-hydroxyprogesterone, 17?-oestradiol, testosterone and 17?-testosterone concentrations in equine oviductal tissue by ultra-HPLC coupled with tandem mass spectrometry, and progesterone, 17?-oestradiol, oestrone and testosterone concentrations in oviduct fluid by radioimmunoassay, with reference to cycle stage and side of ovulation. Progesterone concentrations were high in oviductal tissue and fluid ipsilateral to the ovulation side during dioestrus, whereas other steroid hormone concentrations were not influenced by the side of ovulation. These results suggest that the high ipsilateral progesterone concentration is caused by: (1) contributions from the follicular fluid in the oviduct and diffusion of follicular fluid steroids after ovulation; (2) local transfer of steroids via blood or lymph; (3) local synthesis of progesterone in the oviduct, as evidenced by the expression of steroidogenic enzymes; and (4) a paracrine contribution from follicular cells. These data provide a basis for the study of the importance of endocrine and paracrine signalling during early embryonic development in the horse.

Insulin-like growth factor and insulin-like growth factor-binding proteins in the bovine uterus throughout the oestrous cycle

The aims of the present study were to assess several components of the insulin-like growth factor (IGF) system in bovine uterine flushings across different days of the oestrous cycle and to examine the relationship between the IGF system and systemic progesterone concentrations. Uterine flushings and plasma were collected from cows on Days 3, 7, 11 and 15 of the oestrous cycle. The IGF-1 concentration was more than 5-fold higher in the uterus compared with plasma on Days 7 and 11 of the cycle, with values similar on Days 3 and 15. Similarly, uterine concentrations of IGF-binding protein (IGFBP)-2 and IGFBP-3 were up to 10- and 4-fold higher than in plasma, respectively, suggesting synthesis and/or transportation of the IGFBPs into the uterus. In addition, concentrations of IGFBP-2 and IGFBP-3 were higher in the uterine horns, ipsilateral to the corpus luteum, on Day 15. This difference could indicate a local controlling mechanism with progesterone possibly playing a role in regulating the concentration of IGFBPs between the uterine horns. There was no significant relationship between systemic progesterone concentrations and IGFBP concentrations on Day 7 of the oestrous cycle. The present study shows that uterine concentrations of IGFBPs are cycle stage specific and also suggests IGF-dependent and -independent functions for IGFBPs during a time of major change in the developing embryo.

Spatio-specific regulation of endocrine-responsive gene transcription by periovulatory endocrine profiles in the bovine reproductive tract

In cattle, pro-oestrous oestradiol and dioestrous progesterone concentrations modulate endometrial gene expression and fertility. The aim was to compare the effects of different periovulatory endocrine profiles on the expression of progesterone receptor (PGR), oestrogen receptor 2 (ESR2), oxytocin receptor (OXTR), member C4 of aldo-keto reductase family 1 (AKR1C4), lipoprotein lipase (LPL), solute carrier family 2, member 1 (SLC2A1) and serpin peptidase inhibitor, clade A member 14 (SERPINA14): (1) between uterine horns ipsi- and contralateral to the corpus luteum (CL), (2) between regions of the ipsilateral horn and (3) in the vagina. Endometrium and vagina tissue samples were collected from cows that ovulated a larger (large follicle-large CL, LF-LCL; n=6) or smaller follicle (small follicle-small CL, SF-SCL; n=6) 7 days after oestrus. Cows in the LF-LCL group had a greater abundance of transcripts encoding ESR2, AKR1C4, LPL, SLC2A1 and SERPINA14, but a reduced expression of PGR and OXTR in the endometrium versus the SF-SCL group (PPGR and OXTR was greater in the contralateral compared with the ipsilateral horn (PPGR, ESR2, LPL, SLC2A1 and SERPINA14 (P<0.05). Different periovulatory endocrine profiles, i.e. LF-LCL or SF-SCL, did not influence gene expression in the vagina and had no interaction with inter- or intra-uterine horn gene expression. In conclusion, inter- and intra-uterine horn variations in gene expression indicate that the expression of specific genes in the bovine reproductive tract is location dependent. However, spatial distribution of transcripts was not influenced by distinct periovulatory sex-steroid environments.

Presence of a temperature gradient among genital tract portions and the thermal changes within these portions over the estrous cycle in beef cows

The aim of the present study was to describe the temperature of the different portions of the female genital tract and their relation to rectal temperature and to investigate the effect of steroid hormones profiles on these variables over the estrous cycle in cattle. Four nonpregnant Japanese Black cows were investigated daily over two successive estrous cycles using a digital thermometer with a long probe and rounded-end sensor to record the temperature of the rectum (RT), vagina (VT), cervix (CT), uterine body (UBT) and uterine horns (UHT). Blood samples were collected immediately before temperature recording to assay peripheral levels of progesterone (P(4)) and estradiol-17β (E(2)). Moreover, transrectal ultrasonography was carried out after temperature recording to monitor the ovulatory follicle and track ovulation. During the experiment, the ambient temperature and relative humidity were recorded for further calculation of the temperature humidity index (THI). The temperature within the genital tracts in these cows progressively increased towards the uterine horns from the vagina. The VT, CT, UBT and UHTs were significantly higher in association with peripheral P(4) concentrations greater than 4 ng/ml (mid-luteal phase) when compared with lower peripheral P(4) concentrations. The VT was more significantly (P<0.01) correlated to the CT, UBT and UHTs than RT. In conclusion, a temperature gradient was present among the vagina, cervix and uterus over the estrous cycle, and changes in peripheral P(4) concentrations were associated with the thermal variations within these portions. The VT could be more beneficial than RT in monitoring temperature of deeper portions of the female genital tract in bovine.

Effect of progesterone on embryo survival

Increased genetic selection over the past 40 years has resulted in a dairy cow with an improved biological efficiency for producing milk but with an associated reduced fertility. Embryo loss is the greatest factor contributing to the failure of a cow to conceive. The extent and timing of embryo loss indicates that 70% to 80% of this loss occurs in the first 2 weeks after artificial insemination (AI). This is the period when a number of critical phases in embryo development occur and where protein accretion, substrate utilization and embryo metabolism increase dramatically. During this time the early embryo is completely dependent on the oviduct and uterine environment for its survival and it is likely that the embryo requires an optimal uterine environment to ensure normal growth and viability. There is increasing evidence of an association between the concentration of systemic progesterone and early embryo loss and that progesterone supplementation of cows, particularly those with low progesterone, can reduce this loss. While progesterone is known to affect uterine function and embryo growth, little is known about the uterus during the period of early embryo loss and how this is affected by changes in the concentration of systemic progesterone. The expression of uterine genes encoding the transport protein retinol binding protein (RBP) and the gene for folate binding protein (FBP) appear to be sensitive to changes in systemic progesterone, particularly during the early luteal phase of the cycle. Uterine concentrations of proteins also seem to be regulated by stage of cycle; however, their relationship with the systemic concentration of progesterone is unclear. There is an urgent need to characterize the uterine environment from a functional perspective during the early part of the luteal phase of the cycle, particularly in the high-producing cow, in order to understand the factors contributing to early embryo loss and in order to devise strategies to minimize or reduce this loss.

Ovarian steroids modulate tumor necrosis factor-α and nitric oxide-regulated prostaglandin secretion by cultured bovine oviductal epithelial cells

Ovarian steroids assure an optimum environment for the final maturation of oocytes, gamete transport, fertilization, and early embryonic development. The aim of experiment 1 was to examine the influence of ovarian steroids on tumor necrosis factor-α (TNF-α)- or nitric oxide (NO)-regulated prostaglandin (PG), and nitrite/nitrate (NO₂/NO₃) secretion by cultured bovine oviductal epithelial cells (BOECs). BOECs were pretreated with 17β-estradiol (E₂; 10⁻⁹ M) and/or progesterone (P₄; 10⁻⁷ M) for 24 h. For the next 24 h, BOECs were treated with TNF-α (10 ng/mL) or spermine nitric oxide complex (NONOate; 10⁻⁵ M). Prostaglandin F(2α) and PGE₂ secretion was measured in medium by ELISA. The pretreatment of cells with P₄ (progesterone), E₂ (17 β-estradiol), or E₂/P₄ augmented TNF-α-induced PGF(2α) and PGE₂ secretion (P < 0.01). The pretreatment of cells with E₂ or E₂/P₄ increased NONOate-induced PGF(2α) and PGE₂ secretion (P < 0.01). TNF-α induced NO₂/NO₃ production by BOECs. The pretreatment of cells with E₂ augmented only TNF-α-induced NO₂/NO₃ production (P < 0.05). The aim of experiment 2 was to examine the influence of TNF-α, NO, and ovarian steroids on the protein content of enzymes specifically involved in PG and NO production, PG synthases, and NO synthases (NOSs). BOECs were treated with TNF-α (10 ng/mL) or NONOate (10⁻⁵ M). TNF-α increased the protein content of PGG/H synthase, PGF synthase, and PGE synthase (P < 0.05) and endothelial and inducible NOSs (P < 0.05). Nitric oxide increased the protein content of PGF synthase, PGE synthase, endothelial NOS, and inducible NOS (P < 0.05). These results show possible linkage between TNF-α and NO, modulated by ovarian steroids, in the regulation of PG synthesis by BOECs that may be important for triggering the process of oviductal contractions.

Retinol-binding protein (RBP), retinol and β-carotene in the bovine uterus and plasma during the oestrous cycle and the relationship between systemic progesterone and RBP on day 7

In the dairy cow, low systemic concentrations of progesterone are known to be a major factor associated with early embryo loss. Endometrial expression of the gene encoding retinol-binding protein (RBP) is sensitive to small changes in progesterone on day 7 of the oestrous cycle. The objectives of the present study were to measure RBP concentrations in bovine uterine flushings and plasma across different days of the oestrous cycle and to examine the relationship between uterine RBP and systemic concentrations of progesterone. Uterine flushings and plasma were collected from cows on days 3, 7, 11 and 15 of the oestrous cycle. Uterine RBP concentrations were five- to 15-fold higher (P < 0.001) on day 15 compared with the other days and twofold higher (P < 0.001) in the uterine horn ipsilateral to the corpus luteum on day 15. RBP concentrations were similar in flushings and plasma across days 3-11; however, day 15 RBP concentrations were six- to 15-fold higher (P < 0.001) in uterine flushings. No significant relationship was found between the concentration of systemic progesterone and RBP concentrations on day 7. Overall, the results of the present study indicate a local controlling mechanism operating at the level of the endometrium to regulate RBP secretion, most likely progesterone.

Identification of elevated concentrations of estradiol in bovine uterine endometrium

We have investigated the estradiol content of bovine endometrium and related this to circulating plasma estradiol content. In 9 heifers, mean+/-S.E.M. plasma estradiol concentration was 0.64+/-0.25 pg/ml while the mean+/-S.E.M. endometrial estradiol content was 43.0+/-14.7 pg/g tissue; there was a close relationship between plasma and tissue estradiol levels (R(2)=0.81; P<0.001). During culture of endometrial tissue there was a progressive transfer of estradiol from tissue to culture media but no change in total estradiol. Culture of endometrium from 4 heifers with 5 ng/ml testosterone for 72 h resulted in no increase in estradiol. Furthermore, immunohistochemistry revealed no aromatase protein in uterine endometrium. These results confirm high stored tissue concentrations of estradiol in bovine endometrium while providing no evidence for estradiol synthesis by this tissue. The mechanism(s) through which this sequestration of estradiol into uterine tissue occurs remains to be determined.

Oviductal progesterone concentration and its spatial distribution in cyclic and early pregnant cows

Changes and local distribution of oviductal progesterone (P(4)) concentration during the estrous cycle and early pregnancy in cows were investigated. Intact reproductive tracts were collected from 16 Holstein cows at an abattoir. Samples were classified in to 4 stages (follicular, postovulatory, luteal and early pregnant,< 20 d) based on visual observation of corpus luteum (CL), uterine characteristics and luteal P(4) concentrations. Oviducts were separated from the uterus at the utero-tubal junction and divided into 4 parts: fimbriae, proximal, medial and distal parts. Luteal tissue samples were also collected. Progesterone levels in oviductal and luteal tissues were determined by radioimmunoassay (RIA). Comparatively higher (P < 0.001) P(4) levels were found in stages with a functioning CL ( luteal phase and early pregnancy) than in those with a regressing CL (follicular phase and post ovulation). The oviduct ipsilateral to the CL bearing ovary during the luteal phase and early pregnancy showed higher ( P < 0.001) P(4) concentrations than the contralateral side. Such a difference was not observed during the follicular phase or post ovulation. The ipsilateral oviduct to the functioning CL at early pregnancy showed higher (P <0.05) P(4) levels than at the luteal phase, while no significant difference in luteal P(4) levels between these 2 stages was observed. Neither were any differences in P(4) concentration within the oviduct observed during any phase of the estrous cycle or during early pregnancy. A positive relationship between luteal and oviductal P(4) concentrations was noted. In conclusion, changes in P(4) levels in the oviduct depend on the location and functional stage of the CL. Localized levels of P(4) in the oviduct may be due to local delivery of P(4) from the CL.

The broad ligament: A review of its anatomy and development in different species and hormonal environments

The broad ligament is a double fold of peritoneum forming a mesentery for the human female genital tract. We investigated the anatomy of the broad ligament in different species and its hormonal regulation to determine if it had a role in gonadal positioning. The medical and veterinary literature was reviewed for descriptions of broad ligament anatomy and development. In addition, four adult female rats were dissected to compare the macroscopic anatomy of the broad ligament with any homologous structures in the male (n = 2). Detailed review was made of human males with persistent Müllerian duct syndrome (PMDS) and of bovine freemartin calves to determine the effect of abnormal hormonal environments on broad ligament development. Human and veterinary texts show variable broad ligament development between species, most being consistent with the size and shape of the uterus and uterine tubes. The broad ligament in adult female rats is a simple peritoneal fold and is homologous with the mesentery of the testis and vas deferens in males. Patients with PMDS and bovine freemartins have a broad ligament with intermediate anatomy. In PMDS the broad ligament is elongated and narrow, and not attached to the pelvic wall. The broad ligament is the mesentery of the genital ducts, and its anatomy varies with the degree of Müllerian duct fusion. The absence of a human male homologue is unusual, as the genital mesentery persists in male rodents. Apparent lack of a male homologue in the human may relate to obliteration of the processus vaginalis. The variable development of the broad ligament in pathological conditions is consistent with a role for steroid hormones in its development.

Expression of Cyclooxygenase-2 and Granulocyte-Macrophage Colony-Stimulating Factor in the Endometrial Epithelium of the Cow Is Up-Regulated During Early Pregnancy and in Response to Intrauterine Infusions of Interferon-τ1

On the basis of results obtained in vitro, we previously proposed a model in which signals from the conceptus, namely interferon-tau (IFN-tau) and prostaglandin E2, increase the expression of cyclooxygenase (COX)-2 or granulocyte-macrophage colony-stimulating factor (GM-CSF) in immune and nonimmune cells of the bovine endometrium. Two experiments were conducted to verify the validity of this hypothesis in vivo. In experiment 1, the in vivo expression of COX-2 and GM-CSF during early pregnancy was monitored. Uteri from heifers were collected at different days (d) of the estrous cycle and pregnancy (P). In experiment 2, the effects of intrauterine infusions of IFN-tau on the expression of COX-2 and GM-CSF were analyzed. Immunohistochemistry was performed on uterine sections, and image analysis was used to evaluate the staining intensity in the conceptus, the luminal epithelium (LE), and the subepithelial stroma. In experiment 1, staining for COX-2 was maximal between d18P and d24P, both in the LE and in the conceptus, whereas staining for GM-CSF reached a plateau between d18P and d30P in the LE. In experiment 2, in response to IFN-tau, COX-2 was up-regulated in the LE of the ipsilateral horn, whereas GM-CSF was enhanced in both uterine horns. The current report supports the view that the conceptus, through its secretion of IFN-tau, stimulates maternal epithelial expression of COX-2 and GM-CSF during the peri-attachment period in the cow.

The concentrations of catecholamines and oxytocin receptors in the oviduct and its contractile activity in cows during the estrous cycle

In vitro experiments on oviducts of cyclic cows were undertaken to study: (1) the content of dopamine (DA), noradrenaline (NA) and adrenaline (A) in infundibulum, ampulla and isthmus, (2) the concentration of oxytocin receptors (OTR) in oviductal tissues and (3) the motility of ampulla and isthmus. Changes of DA content were observed in the infundibulum and the ampulla with maximal values occurring on Days 6-10 of the estrous cycle. The mean NA content was greatest in infundibulum<ampulla<isthmus. NA concentrations were the highest in the isthmus on Days 1-5 and 16-21, whereas in infundibulum NA levels were low during the whole estrous cycle. Mean A content was the highest (P<0.001) in the isthmus and in the studied regions of the oviduct A content decreased from Days 1-5 to Days 16-21 (P<0.01). Oxytocin receptors densities were measured in oviducts collected from cows on Days 16-21 (277.1+/-151.4 fmol/mg protein; K(d) 20.5+/-10.9 nM). Oxytocin (10(-7) M) increased the area under the contractile curve (AUC) of the ampulla and the isthmus on Days 16-21 and of the isthmus on Days 1-5 (P<0.01). Acetylcholine (Ach) (10(-7) M) stimulated the ampulla and the isthmus contractions on Days 1-5 (P<0.05) and ampulla contractions on Days 6-10 and 16-21 (P<0.01). NA (10(-5) M) relaxed the ampulla and the isthmus during most of the studied days but was most effective on Days 1-5 and 16-21 (P<0.01).

IN CONCLUSION

(a) catecholamine content in the bovine oviduct varies by region and phase of the estrous cycle, (b) the presence of OTR and the stimulatory effect of oxytocin on oviduct motility are evident in the follicular-phase cows, (c) Ach and NA modify contractile activity in the oviduct of cows during follicular and early-luteal phases and (d) the studied oviductal parameters did not differ by ipsilateral and contralateral relationships to the active ovary in cow.

Dynamic regulation of expression of colony-stimulating factor 1 in the reproductive tract of cattle during the estrous cycle and in pregnancy

Colony-stimulating factor 1 (CSF-1) is a hematopoetic cytokine that also plays an important role in placental physiology. We report here the molecular cloning of two alternative splice variants of the bovine gene coding for a putative secreted and a membrane-bound form of the cytokine and the dynamic regulation of expression in the reproductive tract of cattle during the estrous cycle and pregnancy. Bovine CSF-1 was expressed mainly as the 3- and 4-kilobase (kb) transcripts, but 1.4- and 0.8-kb mRNAs were also detected in Day 50-70 pregnant uterine tissue. During the estrous cycle, both the 4- and 3-kb mRNAs were present, but the 3-kb putative membrane-bound form was more abundant than the 4-kb secreted form during diestrus. This pattern of expression was reversed in pregnancy, so that the exponential increase in CSF-1 expression seen during pregnancy was due predominantly to increased abundance of the 4-kb transcript. The change in the 4-kb:3-kb ratio was detected between Day 14 and Day 17, approximately the time of maternal recognition of pregnancy. Thus, CSF-1 was identified as one gene whose expression in the uterus might be altered early in response to the presence of the conceptus. CSF-1 was also expressed in the extraembryonic membranes of the conceptus and in the trophoblastic cells of the fetal cotyledons after the formation of the placentomes. The high level of CSF-1 expression during bovine pregnancy in uteroplacental tissues is consistent with its proposed role in placental physiology.

Endothelial vasodilator production by uterine and systemic arteries. IX. eNOS gradients in cycling and pregnant ewes

The follicular phase (FOL) and pregnancy exhibit increases in uterine blood flow (UBF), estrogen levels, and uterine artery (UA) endothelial nitric oxide synthase (eNOS) expression. UA branching within the mesometrium increases the total vascular cross-sectional area, which reduces the vascular perfusion pressure gradient, thus locally decreasing the blood flow velocity. Shear stress (SS) activates eNOS and may be associated with UBF elevations during FOL and pregnancy. We hypothesized that regional differences in eNOS responses are observed with both decreases in vessel diameter and during the ovarian cycle and pregnancy. Endothelial isolated proteins were collected from renal (RA) and internal iliac arteries (II) as well as from primary (UA 1 degrees ), secondary (UA 2 degrees), and tertiary (UA 3 degrees) UA branches of nonpregnant luteal phase (LUT; n = 6) and FOL (n = 6) as well as midpregnant (MP; 82 +/- 1 days gestation, n = 6) and late pregnant (LP; 127 +/- 3 days gestation, n = 6) ewes (term = 145 +/- 3 days gestation) for Western blot analysis. LUT RA, II, and UA 1 degrees eNOS levels were similar. There was a 60.7 +/- 9.8% reduction in eNOS expression in UA 2 degrees and UA 3 degrees. A similar decreasing eNOS regional expression gradient was observed in LP ewes. No eNOS regional expression gradient was observed in FOL or MP ewes because eNOS increased in UA 2 degrees and UA 3 degrees. In UA 2 degrees and UA 3 degrees, MP > LP = FOL > LUT. Thus, with increasing UBF, FOL and pregnancy rises in SS may regulate eNOS protein expression in smaller diameter UAs. A decrease in LUT and LP UA 2 degrees and UA 3 degrees endothelial eNOS suggest a possible negative feedback mechanism due to downregulation of eNOS if SS is normalized.

Reproductive loss in high-producing dairy cattle: where will it end?

The dairy industry in the United States has changed dramatically in the last decade. Milk production per cow has increased steadily because of a combination of improved management, better nutrition, and intense genetic selection. Dairy farms are larger, and nearly 30% of the dairy cows in the United States are on farms with 500 or more cows. The shift toward more productive cows and larger herds is associated with a decrease in reproductive efficiency. Cows with the greatest milk production have the highest incidence of infertility, but epidemiological studies suggest that, in addition to milk production, other factors are probably decreasing reproductive efficiency in our dairy herds. The reproductive physiology of dairy cows has changed over the past 50 yr, and physiological adaptations to high milk production may explain part of the reproductive decline. Critical areas for new research include control of the estrous cycle, metabolic effects of lactation on reproduction, mechanisms linking disease to reproduction, and early embryonic mortality. Solving reproductive loss in dairy cows will not be easy because only a small number of research groups study reproduction in postpartum dairy cows. Therefore, the present research base will need to be expanded. For this to occur, research funding must be increased above its current level and a renewed emphasis must be placed on solving the emerging crisis of infertility in dairy cows.

Transuterine embryo migration in recipient cattle

Transuterine migration of bovine embryos following fertilization in vivo is apparently rare, but little is known about migration following embryo transfer. We studied heifers receiving either 1 or 2 in vitro produced embryos to determine 1) the incidence of transuterine migration, 2) the timing of migration and 3) the random or systematic occurrence of the event. In 4 experiments, 436 heifers received embryos and 218 of these were pregnant at necroscopy on either Day 14, Day 18, Day 26 or Day 60 of pregnancy. Overall, 43/218 (20%) of the heifers had embryos that had migrated. The frequency of migration was higher in twin (30/68) than in single (13/150) embryo transfers of pregnant recipients (44 vs 9%; P<0.001), and in contralateral (9/15) than in ipsilateral (33/170) transfers (60 vs 19%; P<0.001). Among the heifers that received embryos by ipsilateral transfer, the migration rate was similar to that in heifers pregnant with a singleton after the transfer of either 1 (2/48) or 2 (4/60) embryos (4 vs 7%, NS). The migration rate was highest at Day 26 (12/37) in heifers receiving twin embryos by ipsilateral transfer but was similar at all other stages of pregnancy (15/111, 32 vs 14%; P<0.01). Migration was first observed by Day 14, and it appears that either further migration occurred over the next 12 d or that migration was associated with a higher survival rate from Day 14 to Day 26. The low migration rate evident at Day 60 suggests that migration by Day 26 was associated with increased embryo or fetal death by Day 60. The data suggest that embryo migration is probably independent for each of a pair of surviving embryos. We conclude that in cattle embryo migration is embryo-dependent, but this capability is dormant unless more than 1 embryo is present in a uterine horn or the embryos are transferred to the contralateral uterine horn. The relationship between migration and embryo survival remains unclear.

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.

The effect of day of the estrous cycle, location of ovulatory structure, and progesterone on in vitro bovine endometrial secretions

Endometrial tissue was collected by biopsy from mature Holstein cows either on d 0 (estrus) or on d 9, 14, or 18 of the estrous cycle to determine the effects of day of the cycle, uterine horn, and in vitro progesterone on endometrial protein secretion. Tissue was incubated for 24 h in supplemented media containing 14C amino acids and either 0, 4.7, or 47 ng of progesterone/ml. Media were analyzed for total protein, radiolabeled protein, and profile of protein released during incubation. Endometrial tissue at d 0 released more protein than did tissue collected on all other days. Radiolabeled proteins were greater on d 0 and 18 than on d 9 and 14. Endometrium from the uterine horn contralateral to the corpus luteum released more radiolabeled protein than endometrium from the uterine horn ipsilateral to the corpus luteum. Seventeen protein bands were identified by electrophoresis. Proximity of the uterine horn to the site of ovulation affected the distribution of specific bands 21,400, 55,000, 74,600, and 88,100 molecular weight. The proportion of released proteins represented by proteins of molecular weights 12,700, 19,100, 21,400, 32,000, and 66,500 was affected either by day of the estrous cycle, proximity of uterine horn to the site of ovulation, or progesterone concentration. The results show that day of the estrous cycle and uterine horn not only alter overall endometrial protein secretion and synthetic activity but also have specific effects on distribution of individual proteins.

Concentrations of nuclear progesterone receptors in endometrium of virgin and repeat breeder heifers after embryo transfer

The present study aimed to correlate the repeat breeder syndrome in the bovine with an impaired or suboptimal uterine progestational response. Concentrations of nuclear (i.e. transformed) receptors for progesterone (PRn) were determined with a binding and exchange method in endometrial samples from virgin (VH) and repeat breeder (RBH) heifers 15 days post oestrus. The heifers were recipients of Day 7 demi-embryos collected from donors with normal fertility and transferred 8 days prior to tissue sampling. Results were compared with both the type of heifer, the condition of the embryo present within the uterus and the temporal relationship to the hormone plasma levels. The binding data for PRn indicated that a single class of high-affinity, low-capacity sites existed. The amount of PRn in VH endometria holding embryonic structures was significantly greater than in RBH, but no statistical differences were found in their plasma progesterone levels. PRn concentrations were also higher in the uterine horn in which an elongated (greater than 15 mm), morphologically normal embryo was present, when compared to cornua with small (less than 5 mm) embryos, regardless of recipient group. Furthermore, in endometria with an elongated embryo in the lumen, the relative amount of PRn was significantly greater in VH than in RBH. The present results indicate that the RBH recipients of Day 7 demi-embryos by Day 15 have fewer numbers of specific receptors for maternal progesterone, which could explain in part the poorer development of the transferred embryos compared with that in virgin heifers.

Protein kinase C in uterine and systemic arteries during ovarian cycle and pregnancy

Elevated uterine blood flow is associated with increases in local estrogen-to-progesterone ratios during the follicular phase of the ovarian cycle and late pregnancy. Because protein kinase C (PKC) activation increases arterial tone, decreased PKC activity may mediate vasodilation. Therefore, we determined uterine (UA) and systemic artery (SA, omental) PKC activity (pmol.mg protein-1.min-1) during the follicular (n = 6), early luteal (n = 4), and late luteal (n = 3) phases of the sheep ovarian cycle, and at 110 +/- 3 (n = 4) and 130 +/- 1 (n = 8) (+/- SE) days of ovine gestation. The stage of the ovarian cycle was verified by the presence of follicles (high estrogen) or corpora lutea (high progesterone) on the ovary and by plasma estrogen and progesterone concentrations. UA-PKC activity (pmol.mg protein-1.min-1) during the follicular phase was 100 +/- 18 and increased progressively to 155 +/- 28 during the early luteal phase and to 219 +/- 37 (P less than 0.05) during the late luteal phase; SA-PKC activity was unchanged. A local utero-ovarian relationship was observed, i.e., UA-PKC activity was lower (P less than 0.001) in UA ipsilateral to ovaries with only follicles (105 +/- 14) when compared with UA adjacent to ovaries with corpora lutea (224 +/- 26), which was similar to SA-PKC activity (184 +/- 35). UA-PKC activity fell from 344 +/- 70 at 110 days to 109 +/- 12 at 130 days gestation (P less than 0.05); SA-PKC activity was unchanged. During the ovarian cycle and latter one-third of ovine pregnancy, increased estrogen production is associated with decreased UA-PKC activity; thus local ovarian and placental steroids may alter PKC activity, thereby regulating UA tone and blood flow.

Alkaline phosphatase activities and progesterone concentrations in uterine flushings of dairy cows: side-effects and variations during oestrous cycle

After evisceration at an abattoir, both uterine horns of barren cows were flushed using 30 ml of Dulbecco's phosphate buffered saline (trial 1, 49 cows) or 10 ml sterile saline (0.9%, trial 2, 22 cows). Blood was collected from the animals' hearts (trial 2). Activities of alkaline phosphatase and progesterone concentrations (trial 2) were determined in uterine flushings and serum. In uterine flushings, both parameters exhibited a significant cyclic pattern, while in serum, only progesterone concentrations showed cyclic fluctuations. Alkaline phosphatase activities in uterine flushings taken ipsilateral to a corpus luteum were significantly higher than in materials obtained from the contralateral horn during dioestrus and prooestrus. A similar tendency was obvious for progesterone concentrations. All parameters but serum alkaline phosphatase activity were positively correlated with each other. The results suggest a close relationship between a progesterone secreting corpus luteum and metabolic as well as hormonal parameters evaluated in flushings of the ipsilaterally situated uterine horn. Transfer of progesterone via the blood vessels and lymphatics within the ligamentum latum uteri may be the cause of the between-side-effects detected.

Activity of alkaline phosphatase in uterine flushings of dairy cows affected with ovarian cysts or endometritis

Both uterine horns of 14 dairy cows with ovarian follicular cysts, and four animals affected with purulent endometritis were flushed via catheter using 30 ml phosphate buffered saline, following evisceration at a local abattori. Activity in the flushing media of alkaline phosphatase (ALP) and aspartate aminotransferase (GOT) were examined. Ovaries were prepared for light microscopy. Amount and morphological integrity of luteinized tissue found on the ovaries were reflected by correspondent levels in ALP activity, which was higher in the media taken from the ipsilateral to the luteal tissue situated uterine horns (651 +/- 228 vs 244 +/- 62 u/l, n = 3). Only cows having relatively large amounts of luteal tissue on the cystic ovaries (as in luteinized follicular cysts) exhibited very high ALP activity in uterine flushings (2693 +/- 1348 u/l, n = 2). Results suggest the existence of local relationships between luteal tissue in the ovary and the ipsilateral uterine horn in cows with ovarian follicular cysts.