Contractile effect of PGF2alpha and PGE2 on isolated branches of uterine and ovarian artery in different days of estrous cycle and early pregnancy in pigs

The contractile effects of PGF2alpha (3 x 10(-6) to 10(-4) M) and PGE2 (10(-7) to 10(-5) M) were examined on isolated branches of ovarian artery (OA) and extramyometrial branches of uterine artery (UA) collected from pigs in the luteal (day 10-12) and follicular phase (day 17-20) of the estrous cycle, and during early pregnancy (day 10-12). Strong contraction was demonstrated in both arteries during all investigated periods in response to PGF2alpha, which was significantly higher (P < 0.01) than to PGE2, being negligible in the follicular phase. In UA, the effective dose of PGF2alpha (ED50) amounted 7.9 x 10(-6) M and 6.3 x 10(-6) M in the luteal and follicular phase, and 5.0 x 10(-6) M in early pregnancy. ED50 for PGE2 reached 5.0 x 10(-7) M in the luteal phase, and 4.1 x 10(-7) M in early pregnancy. For both prostaglandins, the contraction was much stronger (P < 0.01) in OA than in UA branches. In OA, the ED50 for PGF2alpha was 1.2 x 10(-5) M in the luteal phase and was significantly higher (P < 0.05) than in the follicular phase (3.1 x 10(-6) M) and early pregnancy (2.7 x 10(-6) M). ED50 for PGE2 amounted 7.3 x 10(-7) M in the luteal phase and 1.7 x 10(-7) M in early pregnancy. Studies showed the influence of the estrous cycle and early pregnancy on OA branches sensitivity to the contractile effect of PGF2alpha and the lack of this effect on UA branches, and the influence of the estrous cycle on UA and OA branch contraction in response to PGE2.     

Concentrations of ovarian and pituitary hormones following prostaglandin F2 alpha-induced luteal regression in ewes varies with day of the estrous cycle at treatment

Prostaglandin F2 alpha (PGF2 alpha) was injected on d 5, 8 or 11 postestrus in ewes to determine how stage of the estrous cycle would affect PGF2 alpha-induced changes in concentrations of ovarian and pituitary hormones and intervals to the onset of estrus and the preovulatory surge of luteinizing hormone (LH). Initial concentrations of progesterone and average values during the 12 h after PGF2 alpha were related positively to the day of cycle on which PGF2 alpha was administered. Patterns of decline in progesterone after injection of PGF2 alpha were similar among the 3 d. Concentrations of LH in plasma increased in a similar manner from 0 to 12 h in all ewes. After 12 h LH continued to increase, plateaued or declined in ewes treated on d 5, 8 or 11, respectively. Initial concentrations of follicle stimulating hormone (FSH) in plasma were related positively to day of treatment. After treatment with PGF2 alpha, FSH increased within 2 h on d 5 but declined by that time on d 8 or 11. Concentrations of estradiol following treatment did not vary with day. The onset of estrus and the preovulatory surge of LH occurred at 36 and 35, 40 and 45, and 48 and greater than 48 h in ewes treated on d 5, 8 or 11, respectively. It is concluded that: 1) the initial increase in LH is dependent on a decrease in plasma progesterone and 2) differences in patterns of secretion of gonadotropins before the preovulatory surge of LH might be caused by differences in progesterone or progesterone:-estradiol ratio when luteal regression is induced on different days of the estrous cycle.     

Effect of prostaglandin F2 alpha, phenylephrine and ergonovine on uterine contractions in the ewe

Two experiments were conducted to determine the effect of prostaglandin F2 alpha (PGF2 alpha), phenylephrine and ergonovine on uterine contractions. In the first experiment, ewes were bilaterally ovariectomized, and a strain gauge force transducer was sutured to the serosa of one uterine horn. Each ewe was treated sc with 2 micrograms of estradiol-17 beta daily to prevent regression of the uterus. Beginning at least 5 d after ovariectomy, four dose levels of PGF2 alpha, phenylephrine and methoxamine were given by im injection and ergonovine was given by im or iv injection. Phenylephrine, methoxamine and ergonovine are alpha-adrenoceptor agonists. Uterine activity was recorded by physiograph for 30 min before and 90 min after treatment. Tracing were analyzed for 20-min periods before treatment and 4 to 24 min and 50 to 70 min after treatment. In Exp. 2, transducers were attached to uteri of intact ewes at d 10 to 12 of an estrous cycle. During subsequent estrus, one or two dose levels of PGF2 alpha, phenylephrine and ergonovine were given by im injection and uterine activity recorded. In Exp. 1, PGF2 alpha and phenylephrine increased (P less than .05 or .01) the number of amplitude of contractions at both 4 to 24 and 50 to 70 min. Ergonovine given im increased the number of contractions. In intact estrous ewes, PGF2 alpha increased the number and amplitude of contractions at 4 to 24 min, phenylephrine increased the number and amplitude at both 4 to 24 and 50 to 70 min, and ergonovine increased the number slightly but significantly at 4 to 24 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aspects of the antiluteolytic activity of the conceptus during early pregnancy in ewes

Experiments were undertaken to determine whether the conceptus renders a corpus luteum resistant to the luteolytic action of prostaglandin F2 alpha (PGF2 alpha), and modulates release of this prostaglandin by the uterus of early pregnant ewes. Prostaglandin F2 alpha was luteolytic when administered to indomethacin-treated ewes on d 10 and 11 of the estrous cycle. The same PGF2 alpha treatment was not luteolytic when applied on d 19 and 20 of pregnancy in ewes treated with indomethacin. Pulsatile release of PGF2 alpha (measured by 15-keto-13,14-dihydro PGF2 alpha-PGF2 alpha plasma level, PGFM) was observed between d 14 and 16 of the cycle but not during the same period of pregnancy. Ablation of the conceptus on d 17 resulted in progressive restoration of PGFM surges and subsequent luteolysis. Estradiol-17 beta (E2-17 beta) administration on d 12 of the cycle induced earlier PGFM surges and luteal regression. The same E2-17 beta treatment administered on d 14, 19 and 33 of pregnancy failed to induced PGFM pulses and luteolysis. In the absence of the conceptus (surgical ablation), E2-17 beta treatment was luteolytic (PGFM surges) on d 17 but not on d 33. We conclude that the conceptus controls the amount and pattern of PGF2 alpha released by the uterus, as well as the sensitivity of the uterus to E2-17 beta as early as d 14 of pregnancy. Simultaneously, an embryonic protective effect takes place at the luteal level.     

Plasma insulin-like growth factor-I concentrations increase during the estrous phase in goats

The objective of this study was to characterize plasma insulin-like growth factor-I (IGF-I) profiles during the estrous cycle in goats. Frequent blood samples were drawn during the day of estrus and during the luteal phase on Day 10 after estrus, and plasma growth hormone (GH) and IGF-I profiles were examined. Then, daily blood samples were drawn throughout the estrous cycle or during induction of estrus by prostaglandin F(2alpha) (PGF(2alpha)) to further clarify the IGF-I profiles. GH was secreted in an episodic manner in the estrous and luteal phases in goats. There were no significant differences in the mean concentrations, pulse amplitude and pulse frequency of GH between the estrous and luteal phases. IGF-I concentrations during estrous phase were higher than those in the luteal phase (P<0.05). Plasma IGF-I increased approximately two days before behavioral estrus, and the IGF-I peak was observed in accordance with the appearance of estrus. The elevated IGF-I levels then declined to basal values 4 to 5 days after estrus. When estrus was induced by PGF(2alpha), plasma IGF-I concentrations increased after treatment, and the concentration 2 days after treatment (day of appearance of behavioral estrus) was significantly higher than concentrations before treatment (P<0.05). The elevated IGF-I levels then declined during the 3 days after treatment. These results indicate that plasma IGF-I concentrations increase during estrus in goats.     

Effects of feed restriction on reproductive and metabolic hormones in ewes

The goal of this study was to determine the effects of short-term feed withdrawal on reproductive and metabolic hormones during the luteal phase of the estrous cycle in mature ewes. Mature ewes observed in estrus were assigned randomly to control and fasted groups (n = 10 per group Trials 1 and 2). For Trials 1 and 2, control ewes had ad libitum access to feed, whereas fasted ewes were not fed from d 7 through 11 of their estrous cycle; on d 12, all ewes were treated with 10 mg of PGF2alpha, and fasted ewes were gvien ad libitum access to feed. For Trial 1, blood samples were collected daily through fasting and at 2-h intervals following PGF2alpha for 72 h. Serum concentrations of insulin (P < or = 0.002) and IGF-I (P < or = 0.01), but not GH (P > or = 0.60), were decreased during fasting compared with fed ewes. Serum concentrations of 29 (P = 0.02) and 34 kDa (P = 0.04) IGFBP were greater in fasted ewes at 96 h after initiation of fasting than in control ewes. Two control and four fasted ewes in Trial 1 did not exhibit a preovulatory surge release of LH by 72 h. Therefore, Trial 2 was conducted so that the timing of the LH surge could be predicted following the collection of blood samples at 2-h intervals for 112 h and then at 6-h intervals until 178 h following PGF2alpha administration and realimentation. The magnitude of the preovulatory LH surge in Trial 2 was decreased (P = 0.009) and delayed (P = 0.04), and serum concentrations of estradiol were diminished (P < or = 0.03) 12 h before the LH surge in fasted ewes. Ovulation rates were not influenced (P > or = 0.32) by fasting in Trials 1 and 2. Serum concentrations of progesterone in both Trials 1 and 2 were, however, greater (P < 0.001) in fasted than in control ewes. A third trial with ovariectomized ewes was conducted to determine whether the increased serum concentrations of progesterone observed in fasted ewes during Trials 1 and 2 were ovarian-derived. Ovariectomized ewes were implanted with progesterone-containing intravaginal implants and allotted to control (n = 5) or fasted (n = 5) treatment groups and fed as described for Trials 1 and 2. Similar to intact ewes, serum concentrations of progesterone were approximately twofold greater (P < 0.001) in fasted than in control implanted ovariectomized ewes. In summary, feed withdrawal for 5 d during the luteal phase of the estrous cycle increased serum concentrations of progesterone and evoked endocrine changes that could perturb the subsequent estrous cycle.     

The influence of the phase of the estrous cycle on sheep endometrial tissue response to lipopolysaccharide

The effect of lipopolysaccharide on ovine endometrial tissue was examined at estrus (follicular phase) and during the luteal phase. Endometrial tissues were cultured with 0, 1, or 10 microg/mL lipopolysaccharide. After 24 h, culture supernates were harvested and analyzed for PGF2alpha, PGE2, 6-keto-PGF1alpha, thromboxane B2 (TXB2), and cysteinyl-leukotrienes (leukotrienes) using EIA. Homogenates of endometrial tissue were analyzed for prostaglandin endoperoxidase-1 (PTGS-1), and -2 (PTGS-2) as well as Type-I, -II, and -III nitric oxide synthase (NOS) by Western analysis. Follicular phase tissue produced more PGF2alpha (P < 0.001), TXB2 (P < 0.001), and leukotrienes (P < 0.02) than luteal tissue. Lipopolysaccharide increased PGE2 (P < 0.001) and TXB2 (P < 0.02) production by endometrial tissue. Elevations in these eicosanoids were likely due to the measured increases in PTGS-2 (P = 0.002) because no changes in PTGS-1 (P = 0.54) or Type-I, -II, or -III NOS (P > or = 0.20) occurred in endometrial tissue following lipopolysaccharide exposure. These data suggest that the phase of the estrous cycle regulates prostaglandin production by immune-challenged endometrial tissue.     

In vitro investigation of the effects of nonsteroidal anti-inflammatory drugs, prostaglandin E2, and prostaglandin F2alpha on contractile activity of the third compartment of the stomach of llamas

OBJECTIVE: To determine the in vitro effect of prostaglandin (PG) E2, PGF2alpha, and the nonsteroidal anti-inflammatory drugs (NSAIDs) indomethacin, ketoprofen, and nabumetone on the contractile strength of the circular smooth muscle layer of the third compartment of the stomach of llamas. SAMPLE POPULATION: Specimens of the third compartment obtained from 5 healthy adult llamas. PROCEDURE: Full-thickness tissue samples were collected from the third compartment immediately after euthanasia. Specimens were cut into strips oriented along the circular muscle layer and mounted in a tissue bath system. Incremental amounts of ketoprofen, nabumetone, indomethacin, PGE2, and PGF2alpha were added, and contractile strength (amplitude of contractions) was recorded. RESULTS: Generally, PGE2 reduced contractile strength of the circular smooth layer of the third compartment, whereas PGF2alpha, increased the strength of contractions. The activity of the NSAIDs was generally excitatory in a concentration-dependent manner, although significant changes were induced only by administration of indomethacin. CONCLUSIONS AND CLINICAL RELEVANCE: On isolated smooth muscle strips of the third compartment of llamas, exogenous PGE2 and PGF2alpha had a variable effect on contractile strength. Administration of the NSAIDs did not inhibit contractility and would not be likely to induce stasis of the third compartment in the absence of an underlying disease process.     

Regulation of endometrial prostaglandin F(2alpha) synthesis during luteolysis and early pregnancy in cattle

Luteal regression is caused by a pulsatile release of prostaglandin (PG) F(2alpha) from the uterus in the late luteal phase in most mammals including cattle. Although it has been proposed in ruminants that pulsatile PGF(2alpha) secretion is generated by a positive feedback loop between luteal and/or hypophyseal oxytocin and uterine PGF(2alpha), the bovine endometrium may possess other mechanisms for initiation of luteolytic PGF(2alpha) secretion. It has been recently demonstrated that tumor necrosis factor-alpha (TNF-alpha) stimulates PGF(2alpha) output from bovine endometrial tissue not only during the follicular phase but also during the late luteal phase, suggesting that TNF-alpha is a factor in the initiation of luteolysis in cattle. Furthermore, our recent study has shown that IFN-tau suppresses the action of TNF-alpha on PGF(2alpha) synthesis by the bovine endometrium in vitro, suggesting that IFN-tau plays a luteoprotective role by inhibiting TNF-alpha-induced PGF(2alpha) production in early pregnancy. On the other hand, factors other than oxytocin or TNF-alpha have also been suggested to be involved in the regulation of PGF(2alpha) synthesis by bovine endometrium. The purpose of this review is to summarize our current understanding of the endocrine mechanisms that regulate the timing and pattern of uterine PGF(2alpha) secretion during the estrous cycle and early pregnancy.     

Effects of prostaglandin F2 alpha and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance of fluorogestone acetate PMSG-treated ewes

Two experiments were conducted to examine the effect of prostaglandin F2 alpha (PGF2 alpha) and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance (fertility, prolificacy and fecundity) of ewes previously treated with fluorogestone acetate (FGA) and PMSG. In the first experiment, 29 ewes were synchronized for estrus with FGA and PMSG but not bred at the postsynchronization estrus. On day 10 of the first post-synchronization estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to experienced, fertile, raddled rams. Twenty-four of the 29 ewes (83%) had viable fetuses 9 weeks after the PGF2 alpha-PMSG treatment. In the second experiment, 64 ewes were treated with FGA-PMSG, and 33 were exposed to fertile, raddled rams at the synchronized estrus. A second group of 31 ewes was not bred at the synchronized estrus, but on day 12 of the postsynchronized estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to fertile, raddled rams. Sixty-six percent of the 33 ewes lambed in the FGA-PMSG-treated group and 60% of the 31 ewes lambed in the PGF2 alpha-PMSG-treated group. Differences in reproductive performance between these two treatment groups were not statistically significant. The results suggest that the PGF2 alpha-PMSG treatment combination does not adversely affect reproductive performance of ewes.     

In vitro investigation of the effect of prostaglandins and nonsteroidal anti-inflammatory drugs on contractile activity of the equine smooth muscle of the dorsal colon, ventral colon, and pelvic flexure

OBJECTIVES: To determine the in vitro effect of prostaglandin E2 (PGE2), PGF2alpha, PGI2; and nonsteroidal anti-inflammatory drugs (NSAID; ie, flunixin meglumine, ketoprofen, carprofen, and phenylbutazone) on contractile activity of the equine dorsal colon, ventral colon, and pelvic flexure circular and longitudinal smooth muscle. ANIMALS: 26 healthy horses. PROCEDURE: Tissue collected from the ventral colon, dorsal colon, and pelvic flexure was cut into strips and mounted in a tissue bath system where contractile strength was determined. Incremental doses of PGE2, PGF2alpha,, PGI2, flunixin meglumine, carprofen, ketoprofen, and phenylbutazone were added to the baths, and the contractile activity was recorded for each location and orientation of smooth muscle. RESULTS: In substance P-stimulated tissues, PGE2 and PGF2alpha enhanced contractility in the longitudinal smooth muscle with a decrease or no effect on circular smooth muscle activity. Prostaglandin I2 inhibited the circular smooth muscle response with no effect on the longitudinal muscle. The activity of NSAID was predominantly inhibitory regardless of location or muscle orientation. CONCLUSIONS AND CLINICAL RELEVANCE: In the equine large intestine, exogenous prostaglandins had a variable effect on contractile activity, depending on the location in the colon and orientation of the smooth muscle. The administration of NSAID inhibited contractility, with flunixin meglumine generally inducing the most profound inhibition relative to the other NSAID evaluated in substance P-stimulated smooth muscle of the large intestine. The results of this study indicate that prolonged use of NSAID may potentially predispose horses to develop gastrointestinal tract stasis and subsequent impaction.     

Blood flow: a key regulatory component of corpus luteum function in the cow

Prostaglandin F2alpha (PGF2alpha) is the primary luteolysin in the cow. During the early luteal phase, the corpus luteum (CL) is resistant to the luteolytic effect of PGF2alpha. Once mature, the CL becomes responsive to PGF2alpha and undergoes luteal regression. These actions of PGF2alpha coincide with changes in luteal blood flow (BF): PGF2alpha has no effect on BF in the early CL, but acutely increases BF in the peripheral vasculature of the mature CL within 30 min of PGF2alpha injection. During spontaneous luteolysis, luteal BF increases on Days 17-18 of the estrous cycle, prior to any decrease in plasma progesterone (P). The increase in luteal BF is synchronous with an increase in plasma PGFM levels, suggesting that pulsatile release of PGF2alpha from uterus stimulates the increase in luteal BF. Serial biopsies of these CL showed that mRNA expression for endothelial nitric oxide synthase (eNOS) together with endothelin-1 (ET-1) and angiotensin converting enzyme (ACE) increases on Days 17-18 when the luteal BF is elevated. On Day 19 when plasma P level firstly decreases, eNOS mRNA returns to the basal level whereas ET-1 and ACE mRNA remains elevated. Cyclooxygenase-2 (COX-2) mRNA expression increases on Day 19. In support of these data, an in vivo microdialysis study revealed that luteal ET-1 and angiotensin II (Ang II) secretion increases and precedes PGF2alpha secretion during spontaneous luteolysis. In conclusion, we show for the first time that an acute increase of BF occurs in the peripheral vasculature of the mature CL together with increases in eNOS expression and ET-1 and Ang II secretion in the CL during the early stages of luteolysis in the cow. We propose that the increase in luteal BF may be induced by NO from large arterioles surrounding the CL, and simultaneously uterine or exogenous PGF2alpha directly increases ET-1 and Ang II secretion from endothelial cells of microcapillary vessels within the CL, thereby suppressing P secretion by luteal cells. Taken together, our results indicate that an acute increase in luteal BF occurs as a first step of luteolysis in response to PGF2alpha. Therefore, local BF plays a key role to initiate luteal regression in the cow.     

Effects of prostaglandin F2 alpha on degranulation of bovine luteal cells on days 4 and 12 of the estrous cycle

Corpora lutea were collected from 18 beef heifers on day 4 or 12 of the estrous cycle, 1 hour after prostaglandin (PG) F2 alpha or saline (control) treatment. Five heifers also were treated with PGF2 alpha on day 4, but their corpora lutea were not collected until day 12. The relative percentage of cytoplasm occupied by granules decreased only in large luteal cells (LLC) in heifers given PGF2 alpha on day 12, compared with the percentage in controls. Small luteal cells (SLC) were not as affected. The luteal concentration of progesterone was similarly decreased only in heifers given PGF2 alpha on day 12. Treatment of heifers with PGF2 alpha on day 4 had no marked effect on progesterone values or on the relative percentage of cytoplasm occupied by granules in LLC or SLC. Seemingly, LLC were more responsive to PGF2 alpha than were SLC, and PGF2 alpha treatment of beef heifers at day 4 did not markedly impair luteal function.     

黄体期注射PGF2α对母羊血清生殖激素及相关细胞因子的影响

旨在研究黄体期不同阶段注射前列腺激素(PGF2α)对育成母羊生殖激素和生殖相关细胞因子的影响。本研究选择健康、体况良好、体重相近、发情周期正常的湖羊育成母羊60只,用“孕酮栓(MAP)+PMSG”法进行发情周期同步化处理后,选择发情正常的48只母羊随机均分为6组。发情当天记为第0天,黄体前期试验组、中期试验组和末期试验组母羊分别在第6(黄体前期)、11(黄体中期)、16天(黄体末期)注射1 mL PGF2α(0.1 mg),黄体前期对照组、中期对照组和末期对照组母羊分别在第6、11、16天注射1 mL生理盐水,每次注射后0.5、1、2、3 h采血,用于血液指标检测。结果表明,所有试验组和对照组母羊于注射后的0.5~3 h间血清中FSH、LH、PRL、P₄、E₂水平以及TNF-α、IL-1β、IL-6、IFN-β无显著变化(P＞0.05);母羊在黄体期不同阶段注射PGF2α对0.5、1、2、3 h血清中FSH、LH、PRL及IL-1β、IFN-β无显著影响(P＞0.05),前期试验组注射后3 h P₄水平显著低于前期对照组,E₂和IL-6水平显著高于前期对照组(P＜0.05),前期试验组注射后2和3 h TNF-α水平显著高于前期对照组(P＜0.05);中期试验组注射后1 h P₄水平显著低于中期对照组(P＜0.05)。黄体前期注射PGF2α后,前期试验组0.5~ 3 h内FSH、E₂、TNF-α、IL-6整体水平显著高于前期对照组(P＜0.05),P₄整体水平显著低于前期对照组(P＜0.05),对LH、PRL、IL-1β和IFN-β无显著影响(P＞0.05);黄体中期注射PGF2α后,中期试验组0.5~3 h内E₂整体水平显著高于中期对照组(P＜0.05),P₄整体水平显著低于中期对照组(P＜0.05),对FSH、LH、PRL、TNF-α、IL-1β、IL-6和IFN-β无显著影响(P＞0.05);黄体末期注射PGF2α对生殖激素与相关细胞因子没有显著性影响(P＞0.05)。本研究结果表明,PGF2α对黄体的溶解作用存在阶段性差异,母羊在黄体前期对PGF2α的短期应答反应强于黄体中、末期,且黄体前期时,卵巢可以响应PGF2α为卵泡发育营造更佳的发育环境。     

Ovine luteinizing hormone: isoforms in the pituitary during the follicular and luteal phases of the estrous cycle and during anestrus.

Pituitaries were collected from late follicular phase (n = 5), mid-luteal phase (n = 5), and anestrous ewes (n = 4) to assess changes in intrapituitary LH heterogeneity at selected reproductive states. After homogenization, an aliquot of each pituitary extract was desalted by flow dialysis against water and chromtofocused on a pH 10.5 to 4.0 gradient. Concentrations of LH in pituitary extracts and chromatofocusing fractions were determined by RIA. The LH in pituitary extracts resolved into 13 isoforms during chromatofocusing, which were coded with letters beginning with the most basic isoform. Follicular and mid-luteal phase ewes exhibited similar distributions of intrapituitary LH among its isoforms. Relative to follicular and luteal phase ewes, anestrous ewes had lower percentages of isoforms D and E as well as higher percentages of isoforms G, H, J and K. Isoform F, the predominant molecular form of LH, constituted a similar percentage in all treatment groups (P > .05). Thus, the distribution of intrapituitary LH among its isoforms did not change significantly between the mid-luteal and follicular phases of the estrous cycle, but higher percentages of the weakly basic and acidic forms of LH were present during anestrus. These observations suggest that intrapituitary LH heterogeneity changes minimally throughout the estrous cycle of ewes during the breeding season.     

Gonadotropin concentrations, follicular development, and luteal function in pituitary stalk-transfected ewes treated with bovine follicular fluid.

Two experiments, each arranged as a 2 x 2 factorial, were conducted in ewes to examine direct effects of bovine follicular fluid (bFF) on follicular development and luteal function and to further characterize follicular development and luteal function after pituitary stalk transection (SS). In Exp. 1, ewes were sham-operated or SS on d 6 of an estrous cycle and received 5 ml of saline or bFF three times daily on d 5 through 11 of the same cycle. In Exp. 2, all ewes were SS on d 6 of an estrous cycle and treated with saline or bFF three times daily on d 5 through 11 and with ovine FSH (60 micrograms; NIADDK-oFSH-16) or saline (1.2 ml) from d 7 to 11. In Exp. 2, ewes were ovariectomized on d 11 to assess effects of treatments on follicular development and luteal function. In both experiments, concentrations (ng/ml) of FSH on d 7 were suppressed (P less than or equal to .005) by bFF compared with saline (.50 +/- .17 vs 1.63 +/- .15) and remained suppressed (P less than or equal to .005) through d 11 (.46 +/- .12 vs 1.54 +/- .12). Replacement therapy (oFSH) restored concentrations of FSH. Concentrations of LH were not affected by bFF but were elevated (P less than or equal to .05) 1 d after SS (d 7; .88 +/- .09 vs .56 +/- .09) and remained elevated (P less than or equal to .05; 1.31 +/- .20 vs .65 +/- .11) from d 6 through 11. Concentrations of progesterone were unaffected by SS.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of phthalate esters on the secretion of prostaglandins (F2α and E2) and oxytocin in cultured bovine ovarian and endometrial cells

The influence of phthalate esters di-2-ethylhexyl phthalate (DEHP) and mono-2-ethylhexyl phthalate (MEHP) on uterine prostaglandin (PGF2α and PGE2) and ovarian oxytocin secretion was investigated. Endometrial, granulosa, and luteal cells from cows on days 8–12 of the estrous cycle were treated with DEHP or MEHP (0.1, 1, or 10 ng/mL). We found that DEHP and MEHP stimulated (P < 0.05) secretion of PGF2α and inhibited (P < 0.001) secretion of PGE2 from endometrial cells. The ratio of PGF2α to PGE2 was markedly altered. The endocrine disrupting chemicals also enhanced secretion of oxytocin (P < 0.05) from ovarian cells. Our results indicated that DEHP and its metabolite MEHP could affect the process of the estrous cycle by impairing secretion of prostaglandin from the uterus and oxytocin from the ovary.     

The oestrous cycle and early pregnancy--a new concept of local endocrine regulation

Facts discovered in recent decades have compelled us to revise long-established views on the physiological regulation of cyclic adjustments to the reproductive system in preparation for pregnancy in females. Evidence has been presented to show that changes in the uterine blood supply induced by the oestrogen/progesterone ratio in the blood and cytokines are important in the regulation of the secretory function of the endometrium. Progressive reduction in uterine blood flow during the luteal phase of the oestrous cycle causes regressive changes in endometrial cells and release of prostaglandin (PG) F(2 alpha), resulting in initiation of luteolysis. Retrograde transfer of PGF(2 alpha) in the area of the mesometrium vasculature is an important element in the mechanism protecting the corpora lutea against luteolysis before day 12 of the porcine oestrous cycle and during early pregnancy and pseudopregnancy. Results of many studies presented in this review indicate that PGF(2 alpha) pulses in uterine venous blood during the follicular phase of the oestrous cycle may not be due to PGF(2 alpha) secretion by endometrial cells, but occur due to remodeling of the endometrium and pulsatile exretion of PGF(2 alpha) in accordance with rhythmic uterine contractions caused by oxytocin.