Genital tract pressures in mares. I. Normal pressures and the effect of physiological events

A computerised system involving electronic catheter-tipped transducers was used to measure pressures developed within the vagina and uterus of mares. Larger mares tended to have lower intravaginal pressure than ponies. Insertion of an arm into the vagina to place the catheters caused a rise in intravaginal pressure. Pressure in the uterus was usually higher than that in the vagina. Both vaginal and uterine pressures were increased by urination, snorting, whinnying, stretching and respiration - the latter effect was most noticeable in larger mares. Vaginal pressure was also influenced by peristalsis in the rectum, defaecation, the passage of flatus and the stance of the mare.     

The use of catheter-tipped pressure transducers for chronic measurement of genital tract pressures in the ewe. II. Effects of oxytocin and prostaglandin F(2)alpha

Chronic catheterisation of the uterus, ampulla, and abdomen was performed in five ewes using solid-state, catheter-tipped pressure transducers. The catheters remained in place for up to 129 d, allowing in vivo studies of the effects of oxytocin and prostaglandin F(2)alpha (PGF(2)alpha). These agents did not produce any measurable increase in abdominal pressure. Intravenous (i.v.) oxytocin elicited a rapid increase in work done by both the uterus and ampulla. Intramuscular (i.m.) PGF(2)alpha produced a delayed uterine response but little change in the ampulla; i.v. PGF(2)alpha produced a rapid response at both sites. Low plasma progesterone concentrations (< 0.5 ng/ml) were associated with a greater uterine and ampullary response to oxytocin and with an enhanced uterine response to PGF(2)alpha. However, the uterine tube response to intravenous PGF(2)alpha was greatest when plasma progesterone concentrations were high.     

钙调神经磷酸酶信号通路参与前列腺素F2α诱导的心肌肥厚

利用野百合碱（monocrotaline,MCT）诱导大鼠右心室肥厚模型和培养乳鼠心肌细胞,研究前列腺素F2α（prostaglandin F2α,PGF2α）在心肌肥厚中的作用及钙调神经磷酸酶（calcineurin,CaN）信号通路征其中的作用。在雄性Sprague-Dawley大鼠中,用MCT（60mg／kg）单次i．p．诱导右心室肥厚,同时用塞来旨布（20mg／kg）预防／治疗给药2周。用病理检测、电镜观察等方法观察心肌肥厚时组织病理改变;EIA试剂盒检测心肌组织PGF2α含量;RT-PCR检测心房钠尿肽（atrial natriuretic peptide,ANP）和CaNmRNA的表达;用蛋白免疫印迹法检测CaN及其下游因了NFAT3和GATA4蛋门质的表达。以心肌细胞直径、蛋白含量和ANP mRNA表达的变化为0．1μmol／L PGF2α诱导心肌细胞肥大的指标。以CaN mRNA表达作为该信号通路的主要指标,并观察CaN抑制剂环孢素A对PGF2α所致心肌细胞肥人和CaN mRNA表达的影响。结果显示：MCT注射2周（M2W组）,右心室肥厚指数（RVHI）、右心室／体重比及肺重／体重比分别增加了47％、53％和118％;注射后4周（M4W组）增加了64％、94％及156％。电镜观察发现右心室组织损伤。同时,右心室组织PGF2α含量在M2W和M4W组分别增加了44％和51％,与RVHI、ANP和CaN的mRNA表达,及CaN／NFAT3／GATA4的蛋白质表达均呈正相关。环氧酶抑制剂塞来昔布预防和治疗给药均明显改善MCT诱导的组织病理学改变。在高体细胞培养中,PGF2α（0．1μmol／L）明显使心肌细胞增大,蛋白质含量增加,ANP和CaN mRNA表达增强：同时,CaN抑制剂环孢素A明显抑制PGF2α诱导的心肌细胞肥大和CaN mRNA表达。上述结果提示：心肌组织局部PGF2α参与了MCT诱导的心肌肥厚过程,CaN信号通路是其细胞内信号转导通路之一。     

Effect of oxytocin, prostaglandin F2 alpha, and clenbuterol on uterine dynamics in mares

The effects of oxytocin, prostaglandin F2 alpha (PGF2 alpha), and clenbuterol on uterine contractility and tone during anestrus and diestrus, and during mobility and postfixation of the embryonic vesicle were studied in 51 pony mares. Contractility was assessed by scoring real-time ultrasound images, and tone was assessed by transrectal digital compression. Scoring was done by an operator who had no knowledge of treatment assignments. In anovulatory mares primed with progesterone for 16 d, oxytocin did not significantly alter contractility but did stimulate an increase in tone, whereas clenbuterol depressed both contractility and tone. The PGF2 alpha given on Days 12, 15, and 18 did not significantly alter uterine contractility in pregnant mares, but it increased contractility on all days in nonpregnant mares. Clenbuterol decreased both tone and contractility when given to pregnant mares on the day of embryonic-vesicle fixation, while it decreased tone but not contractility when given on Day 19. Clenbuterol treatment was associated with dislodgment of the fixed embryo in only 1 of 5 mares. However, on Day 19, clenbuterol treatment was associated with a change in shape of the conceptus when viewed in a cross section of the uterine horn. The conceptus shape became more circular rather than irregular or triangular, as indicated by a significant decrease in the variation in the distances between adjacent walls measured in 4 different directions. Results indicated that: 1) oxytocin increased uterine tone but did not alter contractility in progesterone-primed anestrous mares; 2) on Days 12, 15 and 18, PGF2 alpha increased uterine contractility in nonpregnant mares but not in pregnant mares; 3) clenbuterol decreased both tone and contractility at all reproductive states except for a lack of a decrease in contractility on Day 19 of pregnancy; and 4) reduction in uterine tone from clenbuterol treatment on Day 19 was associated with a change in the two-dimensional shape of the in situ conceptus from irregular to a more circular form.     

Changes in the plasma prostaglandin F2 alpha metabolite before and during spontaneous labor and labor induced by amniotomy, oxytocin and prostaglandin E2

To elucidate the role of endogenous prostaglandin F2 alpha in spontaneous and induced labor, plasma concentrations of 13, 14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were determined before the onset of labor, at onset of labor, during active labor, at the crowning of the fetal head, and 1 and 2 hours after delivery. Patients in spontaneous labor and labor induced by amniotomy, oxytocin, and prostaglandin E2 were studied. The levels of plasma PGFM in patients who entered spontaneous labor fell 2 to 3 weeks before delivery, whereas those in the induced labor group did not change until the time of induction. Although the levels of PGFM rose gradually with the progress of labor in all cases, the levels in the spontaneous labor were significantly lower in each stage than in the corresponding stage of induced labor. These results suggest that endogenous prostaglandin F2 alpha (PGF2 alpha) production decreases 2-3 weeks prior to the spontaneous onset of labor and is increased again as labor progresses, that the patterns of PGF2 alpha production are similar to each other during spontaneous labor and labor induced by various methods. Therefore, it is felt that endogenous PGF2 alpha may participate in the progress of all kinds of labor.     

Acute effects of prostaglandin F(2alpha) on systemic oxytocin and progesterone concentrations during the mid- or late-luteal phase in mares

The acute effects of prostaglandin F(2alpha) (PGF) on circulating oxytocin and progesterone concentrations were characterized in mares during the mid- or late-luteal phase. Pony mares were randomly assigned to the following experimental groups based on treatment with PGF (2.5mg) or saline on Day 8 or Day 13 (Day 0=ovulation): PGF-8, PGF-13, saline-8, or saline-13 (n=7/group). Mares were fitted with indwelling, jugular vein catheters and two blood samples (-5 and 0 min) were collected prior to treatment. Treatments were administered into the jugular vein (0 min) and blood collection continued thereafter at 1 min intervals until 5 min and then at 5 min intervals until 60 min. Based on the combined data of -5 and 0 min samples, mares on Day 8 had greater (P<0.05) oxytocin concentrations than mares on Day 13. On Day 8, PGF treatment resulted in a biphasic pattern of oxytocin release. Oxytocin concentrations increased (P<0.05) 1 min after PGF treatment, decreased (P<0.05) from 1 to 10 min, and increased (P<0.05) from 10 to 30 min. Oxytocin concentrations were greater (P<0.05) from 1 to 3 min in PGF-treated than saline-treated mares and at most sample times from 15 to 60 min. On Day 13, oxytocin concentrations were greater (P<0.05) in PGF-treated than in saline-treated mares for most sample times. Mares treated with PGF on Day 8 had greater (P<0.05) oxytocin concentrations at 25, 30, and 40 min than mares on Day 13. Progesterone concentrations on Day 8 also increased by 1 min after PGF, decreased toward basal concentrations by 2-3 min, and then increased to a maximum 10 min after treatment. Subsequently, circulating progesterone decreased (P<0.05) below pretreatment concentrations by 40-50 min after PGF. In conclusion, treatment with PGF resulted in an immediate and biphasic increase in progesterone concentrations prior to the expected decrease. Treatment of mares with PGF on Day 8 resulted in an overall greater increase in systemic oxytocin concentrations compared to treatment on Day 13, and the increase on Day 8 was biphasic.     

Changes in steady-state concentrations of messenger ribonucleic acids in luteal tissue during prostaglandin F2alpha induced luteolysis in mares

Transvaginal ultrasound-guided luteal biopsy was used to evaluate the effects of prostaglandin (PG)F2alpha on steady-state concentrations of mRNA for specific genes that may be involved in regression of the corpus luteum (CL). Eight days after ovulation (Hour 0), mares (n=8/group) were randomized into three groups: control (no treatment or biopsy), saline+biopsy (saline treatment at Hour 0 and luteal biopsy at Hour 12), or PGF2alpha+biopsy (5mg PGF2alpha at Hour 0 and luteal biopsy at Hour 12). The effects of biopsy on CL were compared between the controls (no biopsy) and saline+biopsy group. At Hour 24 (12h after biopsy) there was a decrease in circulating progesterone in saline group to 56% of pre-biopsy values, indicating an effect of biopsy on luteal function. Mean plasma progesterone concentrations were lower (P<0.001) at Hour 12 in the PG group compared to the other two groups. The relative concentrations of mRNA for different genes in luteal tissue at Hour 12 was quantified by real time PCR. Compared to saline-treated mares, treatment with PGF2alpha increased mRNA for cyclooxygenase-2 (Cox-2, 310%, P<0.006), but decreased mRNA for LH receptor to 44% (P<0.05), steroidogenic acute regulatory protein to 22% (P<0.001), and aromatase to 43% (P<0.1) of controls. There was no difference in mRNA levels for PGF2alpha receptor between PG and saline-treated groups. Results indicated that luteal biopsy alters subsequent luteal function. However, the biopsy approach was effective for collecting CL tissue for demonstrating dynamic changes in steady-state levels of mRNAs during PGF2alpha-induced luteolysis. Increased Cox-2 mRNA concentrations suggested that exogenous PGF2alpha induced the synthesis of intraluteal PGF2alpha. Thus, the findings are consistent with the concept that an intraluteal autocrine loop augments the luteolytic effect of uterine PGF2alpha in mares.     

Route of prostaglandin F2alpha injection and luteolysis in mares (38519).

Nine groups of pony mares (3/group) were used in a 3 times 3 factorial experiment. The factors were dose of PGF-2 alpha (0, 0.25 of 1.25 mg and route of administration (im, iu or il). Mares were laparotomized and treated on day 7 postovulation. Jugular blood was collected for progesterone RIA at 0 (pretreatment) and 1,6,12,24,48, and 72 hr posttreatment. In mares given either 0.25 mg or 1.25 mg PGF-2alpha, progesterone concentrations were not significantly different among the three routes at any of the posttreatment times studied except at 6 hr posttreatment. In mares given 0.25 mg, progesterone concentrations at 6 hr was less (p less than 0.05) for mares injected im than for mares injected iu. Compared to pretreatment progesterone values, PGF2-alpha (0.25 mg and 1.25 mg groups combined) administration significantly decreased progesterone concentration by 12 hr posttreatment in mares injected im and 24 hr in mares injected iu or il. In the iu group, a significant increase in progesterone concentration occurred between 1 and 6 hr followed by a significant decrease at 12 hr posttreatment. There were no significant differences among the three routes for intervals from treatment to estrus or ovulation, length of posttreatment estrus or length of interovulatory interval. Injection of either 0.25 mg or 1.25 mg PGF-2alpha significantly shortened the interval from treatment to estrus. Although 0.25 mg tended to shorten the interval from treatment to ovulation and interovulatory interval, these two end points were significantly shortened only in mares given 1.25 mg PGF-2alpha. Results indicated that local administration (iu or il) did not improve the luteolytic efficacy of PGF-2alpha over systemic administration (im).     

Farrowing induction with a combination of prostaglandin F(2alpha) and a peripherally acting alpha(2)--adrenergic agonist AGN 190851 and a combination of prostaglandin F(2alpha) and oxytocin

We studied the effect of prostaglandin (PG) F(2alpha)-AGN 190851 on farrowing induction and compared it with that of PGF(2alpha)-oxytocin. Eighty crossbred, multiparous sows were randomly assigned to the following 4 treatment groups of 20 sows each: 1) control, saline-saline; 2) PGF(2alpha) (10 mg/sow)-oxytocin (30 IU/sow); 3) PGF(2alpha) (10 mg/sow)-AGN 190851 (0.06 mg/kg); and 4) PGF(2alpha) (10 mg/sow)-AGN 190851 (0.1 mg/kg). Either PGF(2alpha) or saline was administered intramuscularly on Day 111 of gestation at 11:30 h; AGN 190851, oxytocin or saline was administered intramuscularly 20 h after the first injection. The PGF(2alpha)-AGN 190851 (0.1 mg/kg) treated sows had the shortest mean farrowing interval (2.1 +/- 1.6 h, mean +/- SD) compared with the remaining treatment groups (control: 67.1 +/- 26.2 h; PGF(2alpha)-oxytocin: 5.6 +/- 6.7 h; PGF(2alpha)-AGN 190851 [0.06 mg/kg]: 3.0 +/- 2.8 h). Duration of farrowing, litter size, litter weight and interval from weaning to first estrus in sows were not significantly changed by these treatments. The PGF(2alpha)-oxytocin group had a significantly higher stillbirth rate than the control group, whereas the PGF(2alpha)-AGN 190851 (0.1 mg/kg) group had the lowest number of pigs born dead and stillbirth rate among the 4 treatment groups. These results suggested that the PGF(2alpha)-AGN 190851 combination can be used as an alternative method to PGF(2alpha)-oxytocin for synchronizing farrowing.     

Induction of parturition in swine with prostaglandin F(2)alpha, estradiol benzoate and oxytocin

Pregnant sows and gilts were administered either 0, 2.5, 5, 10 or 20 mg prostaglandin F(2)alpha (PGF(2)alpha) intramuscularly on Day 112 or 113 of gestation at 0800 h in an effort to induce parturition. The average interval from PGF(2)alpha injection to farrowing was 55.1 +/- 5.7, 29.4 +/- 3.1, 32.1 +/- 4.6, 27.8 +/- 1.8 and 26.9 +/- 1.1 h for 0, 2.5, 5, 10 and 20 mg, respectively. All PGF(2)alpha treatments increased (P < 0.01) over controls the number of sows farrowing 23 to 33 h after injection. The average gestation length was significantly shorter in treated gilts; however, no detrimental effect on pig performance or pig survivability was observed. A second trial evaluated the effect of a 10-mg dose of PGF(2)alpha on the induction of parturition in sows in order to obtain a majority of sows farrowing within normal working hours (0700 to 1700 h). The interval from injection to farrowing was decreased (P < 0.05) by PGF(2)alpha treatment (66.2 +/- 5.3 vs 28.1 +/- 2.2 h). Fifty-seven percent (P < 0.05) of PGF(2)alpha-treated sows farrowed between 0700 and 1700 h as compared to 13.6% for control sows. A third trial was conducted to examine a sequential treatment of PGF(2)alpha and oxytocin to control the time of parturition more precisely. Sows receiving only 10 mg of PGF(2)alpha farrowed on an average 31.1 +/- 1.4 h after injection. The injection of 40 IU oxytocin 24 to 28 h after PGF(2)alpha decreased (P < 0.05) the interval from PGF(2)alpha to farrowing (28.1 +/- 0.9 h). The addition of oxytocin increased (P < 0.05) the number of sows farrowing within 3 h of injection (33 vs 86% for PGF(2)alpha and PGF(2)alpha + oxytocin treatments, respectively). A fourth trial was designed to determine if the addition of exogenous estradiol benzoate (EB) to a sequential treatment of PGF(2)alpha and oxytocin would improve the predictability and synchronization of the induced parturition. Sows were assigned to receive either saline, 10 mg PGF(2)alpha + 40 IU oxytocin or 10 mg PGF(2)alpha + 5 mg EB + 40 IU oxytocin. The addition of EB reduced (P < 0.01) the variance in the interval from oxytocin to farrowing and added precision to the predicted time of induced parturition.     

Uterine responsiveness of oxytocin and prostaglandin F2 alpha in heat-acclimated rats

1. Contractility, in vitro, was examined in uterine horns of rats acclimated to 35 degrees C and controls (22 degrees C). 2. Responses to oxytocin and prostaglandin F2 alpha were measured in the four stages of the estrus cycle and on day 4 of pregnancy. 3. Responses to oxytocin of uteri from heat acclimated rats were significantly depressed in estrus, metestrus and diestrus, while responses to prostaglandin F2 alpha were decreased in estrus and metestrus. 4. Responses to oxytocin and prostaglandin were slightly but insignificantly decreased in uteri from pregnant day 4 heat-acclimated rats.     

Embryonic loss in mares: Nature of loss after experimental induction by ovariectomy or prostaglandin F(2alpha)

Twenty-one pregnant pony mares were assigned to one of the following groups: 1) controls, 2) ovariectomy at Day 12, 3) ovariectomy at Day 12 plus daily progesterone treatment on Days 12 to 40, 4) PGF(2alpha) on Day 12, 5) PGF(2alpha) on Day 21, and 6) PGF(2alpha) on Day 30. Based on daily examinations by ultrasound, the embryonic vesicle was maintained to Day 40 in all control mares and in mares that were ovariectomized on Day 12 and given progesterone. The embryonic vesicle was lost in all mares of the other four groups. Administration of progesterone prevented the embryonic loss associated with ovariectomy at Day 12, indicating that progesterone may be the only ovarian substance required for survival of the early embryo. The mean number of days to embryonic loss was greater for mares treated with PGF(2alpha) on Day 12 (6.8 days) than for mares ovariectomized on Day 12 (3.0 days). In the PGF(2alpha)-treated group, the vesicles did not become fixed at the expected time (Day 15), and mobility continued until the day of loss. In the mares treated with PGF(2alpha) on Day 21 and in one of the mares treated on Day 30, the vesicle was lost within one to three days without prior indication. Loss may have occurred by expulsion through the cervix, since the cervix was patent on the day of loss in these mares and in the mares ovariectomized or treated with PGF(2alpha) on Day 12. In the remaining mares treated on Day 30, the intact embryonic vesicle was dislodged on Day 31 or 32. The dislodged vesicle was mobile within the uterus and was frequently found in the uterine body. The fluid volume of the dislodged vesicle gradually decreased, and the fluid was no longer detected by Day 38 to 42. Some of the placental fluids may have been eliminated by resorption since the cervix remained closed while the fluid volume decreased.     

Changes in ovarian oxytocin secretion as an indicator of corpus luteum response to prostaglandin F(2alpha) treatment in cattle

Exogenous prostaglandin F(2alpha) (PGF(2alpha)) rapidly increases ovarian oxytocin (OT) release and decreases progesterone (P4) secretion in cattle. Hence, the measurement of OT secretion (the area under the curve and the height of the peak) after different doses of Oestrophan - PGF(2alpha) analogue (aPGF(2alpha)) on Days 12 and 18 of the estrous cycle (estrus = day 0), could be a suitable indicator of corpus luteum (CL) sensitivity to PGF(2alpha) treatment. Mature heifers (n = 36) were used in this study. Blood samples were collected from the jugular vein for the estimation of OT, P4 and 13, 14-dihydro-15-keto-prostaglandin F(2alpha) (PGFM). In Experiment 1, different doses of aPGF(2alpha) (400, 300, 200 and 100 microg) given on Day 12 of the estrous cycle (n = 8) shortened (P < 0.05) the cycle duration (15.2 +/- 0.6 d) compared with that of the control (21.7 +/- 0.4 d). Successive heifers were also treated on Day 12 with 200 (n = 2), 100 (n = 2), 75 (n = 2) or 50 microg aPGF(2alpha) (n = 2). Only the 50 microg aPGF(2alpha) dose did not cause CL regression, although it increased OT concentrations to levels comparable to those observed during spontaneous luteolysis (50 to 70 pg/ml). In Experiment 2, on Day 18 of the cycle heifers (n = 8) were treated with 50, 40, 30 and 20 microg aPGF(2alpha). There was a dose-dependent effect of aPGF(2alpha) on OT secretion on Day 18 of the estrous cycle (r = 0.77; P < 0.05). In Experiment 3, an injection of 500 microg aPGF(2alpha) on Day 12 (n = 4) and 50 microg aPGF(2alpha) on Day 18 (n = 4) caused a similar (P > 0.05) increase in the OT concentration (288.5 +/- 23.0 and 261.5 +/- 34.7 pg/ml, respectively). Thus the effect of the same dose of aPGF(2alpha) (50 microg) on OT secretion was different on Days 12 and 18 of the cycle. To evoke similar OT secretion on Days 12 and 18 the dose of aPGF(2alpha) on Day 18 could be reduced 10-fold, confirming that CL sensitivity to PGF(2alpha) appears to increase in the late luteal phase.     

Study of oxytocin receptor: II. oxytocin and prostaglandin F2 alpha receptors in human myometria and amnion-decidua complex during pregnancy and labor

Oxytocin receptors (OXT-R) and prostaglandin F2 alpha receptors (PGF2 alpha-R) in human myometrium, amnion and decidua during pregnancy and at parturition were examined in an effort to clarify their role in the initiation and maintenance of uterine contractions. The number of binding sites for OXT in myometria showed an increase as gestation advance (Ist trimester v.s. at term; 205 +/- 90 v.s. 671 +/- 98 fmol/mg protein, N = 5, p less than 0.01), and a rapid decrease following the onset of labor (254 +/- 60 fmol/mg protein, N = 5, p less than 0.02). On the other hand the number of PGF2 alpha-R, remained unchanged throughout pregnancy and in labor. This myometrial PGF2 alpha binding capacity was approximately 1/20 to 1/30 that of the OXT binding, while binding affinity was almost equal. The OXT-R both in amnion and decidua, which was 1/6 to 1/7 that in myometrium, showed no significant changes throughout pregnancy or after the onset of labor. Binding affinity for each tissue was almost the same and appeared to increase towards term but no statistical significance was detected. Present data confirmed the presence of OXT as well as PGF2 alpha receptors in the three functionally distinct entities of pregnant human uterus; myometrium, amnion, and decidua. Among the components, the OXT binding increased only in the myometrium during pregnancy, suggesting this tissue specifically responds to OXT. In contrast, there was a constant binding in myometria for PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in human plasma catecholamines and dopamine-beta-hydroxylase produced by prostaglandin F2 alpha

Clinical research was conducted into the possible interrelationships between prostaglandin (PG) F2alpha and the human sympathetic nervous system. The study also permitted comparison of the relative sensitivity of 2 indicators of sympatho-adrenal activity: 1) the determination of circulating catecholamines, epinephrine and norepinephrine; and 2) analysis of plasma dopamine-8-hydroxylase activity. Intravenous PGF2alpha infusion was administered to college students 12-18 weeks pregnant to produce abortion; the results were compared to results from nonpregnant controls. Circulating norepinephrine but not plasma epinephrine or dopamine-8-hydroxylase levels were increased in response to the PG. There was no correlation between plasma epinephrine and plasma norepinephrine levels. Plasma dopamine-8-hydroxylase activity was found not to be significantly changed by pregnancy, administration of the analgesic and antiemetic, or the PG infusion. In fact, central venous dopamine-8-hydroxylase activity did not differ significantly from that of arterial blood. The PG did not affect cardiac output or maximal expiratory flow rate. It is suggested that the nausea and diarrhea accompanying PGF2alpha infusion may put stress on the sympathetic nervous activity causing the observed increase in plasma norepinephrine concentration. Since no changes in blood pressure, heart rate, central venous pressure, or cardiac output were observed, it is unlikely that PGF2alpha causes even slight impairment of sympathetic nervous system activity.     

Timing of prostaglandin F(2alpha) release episodes and oxytocin receptor development during luteolysis in the cow

The timing of PGF(2alpha) release and the timing and extent of the rise in endometrial oxytocin receptors was determined in relation to the timing of the progesterone fall during luteolysis in cycling cows. In cows undergoing luteolysis (n = 6), measurement of PGF(2alpha) metabolite in hourly plasma samples collected during daily 10 h sampling periods identified a total of 2.2+/-0.5 PGF(2alpha) release episodes per animal, each of 4.0+/-0.4 h duration. In cows in which luteolysis was not observed (n = 4) no PGF(2alpha) release episodes were identified. In a further three cows in which additional repeated uterine biopsies were collected on days 15, 17, 19, 21 and 23, endometrial oxytocin receptors were initially undetectable (<15 fmol/mg protein) but had increased to 120+/-19 fmol/mg protein prior to the initiation of PGF(2alpha) release episodes. Receptor concentrations then continued to increase reaching peak concentrations of 651+/-142 after luteolysis had been completed.     

Estrous cycle characteristics, luteal function, secretion of oxytocin (OT) and plasma concentrations of 15-keto-13,14-dihydro-PGF2alpha (PGF2alpha-metabolite) after administration of low doses of prostaglandin F2alpha (PGF2alpha) in pony mares

In the present study, the kinetics of the prostaglandin F2alpha (PGF2alpha)-metabolite 15-keto-13,14-dihydro-PGF2alpha after a single intramuscular application of various doses of the natural PGF2alpha dinoprost at Day 7 of the cycle in the mare were investigated. Effects of low doses on estrous cycle length and life span of corpus luteum were examined, because release of PGF2alpha is still under discussion to have detrimental influence on success rates of transcervical transfer of equine embryos. Eight Shetland pony mares were each randomly assigned to each of four treatments: (a) 0.8 mg/100 kg (group T1), (b) 0.4 mg/100 kg (group T2), (c) 0.2 mg/100 kg BM dinoprost i.m. (group T3), and (d) 1 ml physiological saline i.m. (group CO). Treatments were administered as single doses on Day 7 of the estrous cycle. Administration of dinoprost caused dose-dependent rises of plasma concentrations of PGF2alpha-metabolite, although values of individual mares showed great variation within groups. Prostaglandin treatments resulted in a distinct decrease of plasma progesterone concentrations to values between 1.6 and 7.9 ng/ml within 24 h. Treatment groups had significantly lower progesterone area under the curve (AUC: T1 942.8+/-175.9, T2 1050+/-181.2 and T3 1117+/-179.8 ng/ml/h) when compared with controls (CO 1601.9+/-227.6; t-test, P<0.05 ). There was a small, but significant negative correlation between AUC of progesterone and of PGF2alpha-metabolite ( R=-0.4; P=0.05 ). Administration of PGF2alpha caused secretion of oxytocin in three (T1, T2) and two (T3) mares out of eight ranging from 19.3 to 63.1 pg/ml. The AUC of oxytocin was positively correlated with AUC of PGF2alpha-metabolite ( R=0.4, P<0.05) and negatively correlated with AUC of progesterone ( R=-0.4, P<0.05). Administration of dinoprost yielded significantly shorter intervals from treatment to estrus and ovulation (values in parentheses), respectively, when compared with controls: T1 3.9+/-0.7 days ( 12.1+/-0.7 days), T2 4.5+/-0.6 ( 12.3+/-0.6 ), T3 4.9+/-0.5 ( 12.3+/-0.6 ), and CO 8.9+/-0.6 days ( 16.5+/-0.8 days) (t-test, P<0.01 ) (Fig. 2). Different doses of PGF2alpha caused similar effects. Data suggest that progesterone concentrations at applications influence efficacy of treatments more than doses administered, as demonstrated by their high correlation with estrous cycle patterns. It is important to note that differences we achieved are gradual and that all mares responded to treatment by luteolysis and premature estrus, regardless of doses applied.     

Coupling between cyclooxygenases and prostaglandin F(2alpha) synthase. Detection of an inducible,glutathione-activated,membrane-bound prostaglandin F(2alpha)-synthetic activity

Distinct functional coupling between cyclooxygenases (COXs) and specific terminal prostanoid synthases leads to phase-specific production of particular prostaglandins (PGs). In this study, we examined the coupling between COX isozymes and PGF synthase (PGFS). Co-transfection of COXs with PGFS-I belonging to the aldo-keto reductase family into HEK293 cells resulted in increased production of PGF(2alpha) only when a high concentration of exogenous arachidonic acid (AA) was supplied. However, this enzyme failed to produce PGF(2alpha) from endogenous AA, even though significant increase in PGF(2alpha) production occurred in cells transfected with COX-2 alone. This poor COX/PGFS-I coupling was likely to arise from their distinct subcellular localization. Measurement of PGF(2alpha)-synthetic enzyme activity in homogenates of several cells revealed another type of PGFS activity that was membrane-bound, glutathione (GSH)-activated, and stimulus-inducible. In vivo, membrane-bound PGFS activity was elevated in the lung of lipopolysaccharide-treated mice. Taken together, our results suggest the presence of a novel, membrane-associated form of PGFS that is stimulus-inducible and is likely to be preferentially coupled with COX-2.