The use of PGF2α as ovulatory stimulus for timed artificial insemination in cattle

The objective of this study was to evaluate the effect of a PGF2α-analogue (PGF) on ovulation and pregnancy rates after timed artificial insemination (TAI) in cattle. In experiment 1, crossbred dual-purpose heifers, in a crossover design (3 × 3), were given an intravaginal progesterone-releasing insert (controlled internal drug release [CIDR]) plus 1 mg estradiol benzoate (EB) intramuscularly (im) and 250 μg of a PGF-analogue im on Day 0. The CIDR inserts were removed 5 days after follicular wave emergence, and the heifers were randomly divided into three treatment groups to receive the following treatments: (1) 1 mg of EB im (EB group, n = 13); (2) 500 μg of PGF im (PG group, n = 13); or (3) saline (control group, n = 13), 24 hours after CIDR removal. Ovulation occurred earlier in EB (69.81 ± 3.23 hours) and PG groups (73.09 ± 3.23 hours) compared with control (83.07 ± 4.6 hours; P = 0.01) after CIDR removal. In experiment 2, pubertal beef heifers (n = 444), 12 to 14 months of age were used. On Day 0, the heifers were given a CIDR insert plus 2 mg EB im. On Day 9, the CIDR was removed and the heifers were given 500 μg of PGF im. Heifers were randomly assigned into one of three treatment groups: (1) 1 mg of EB (EB group; n = 145); (2) 500 μg of PGF (PG group; n = 149), both 24 hours after CIDR removal; or (3) 600 μg of estradiol cypionate (ECP group; n = 150) at CIDR removal. Timed artificial insemination occurred 48 hours after CIDR removal in the ECP group and 54 hours in the PG and EB groups. The percentage of heifers ovulating was higher in the PG group compared with the other groups (P = 0.08). However, the pregnancy rates did not differ among groups (47.6%, 45%, and 46.6%, for EB, PG, and ECP, respectively; P = 0.9). In experiment 3, 224 lactating beef cows, 40 to 50 days postpartum with 2.5 to 3.5 of body condition score were treated similarly as described in experiment 2, except for the ECP group, which was excluded. The treatments were as follows: 1 mg EB (EB group; n = 117) or 500 μg PGF (PG group; n = 107), 24 hours after CIDR removal. The calves were temporarily separated from their dams from Days 9 to 11. No difference was detected on the pregnancy rate between the EB and PG groups (58.1% vs. 47.6%, respectively; P = 0.11). Taken together, the combined results suggested that PGF2α could be successfully used to induce and synchronize ovulation in cattle undergoing TAI, with similar pregnancy rates when compared with other ovulatory stimuli (ECP and EB).     

Effect of uterine luminal perfusion of PGF2α and PGE2 on uterine vasomotor response and PGF2α output in cyclic cattle

Six cyclic Holstein dairy cows were anesthetized on days 12–14 post-oestrus. Reproductive tract was exposed by midventral incision, and the ovarian (utero-ovarian) vein and facial artery cannulated. Oviduct was ligated, and a catheter (affluent) introduced into the tip of the uterine horn. The uterine horn was ligated above the uterine body, a second catheter (effluent) introduced into the uterine lumen, and an electromagnetic blood flow transducer placed around the uterine artery. On the day following surgery, the uterine horn was infused constantly for 9 h with PGF_2α dissolved in PBS (0.7 ml/min, 177 ng/ml). During periods 1 and 3 (first 3 h and last 3 h, respectively) only PGF_2α was perfused; during period 2 (between 3 h and 6 h) 101tgμg/ml of PGE₂ were added to the perfusate together with PGF_2α. Uterine venous and peripheral blood samples were collected simultaneously every 15 min, and uterine blood flow recorded continuously. Least-square means for PGF measured in uterine venous drainage for periods 1, 2 and 3 were 315 ± 26, 557 ± 24 and 511 ± 26 pg/ml, respectively (P < 0.05). Uterine blood flow values were 52 ± 5, 67 ± 4 and 61 ± 4 ml/min for periods 1, 2 and 3 (P < 0.08), respectively.Results do not support the hypothesis that the antiluteolytic effect of PGE₂ is associated with a suppression of uterine PGF_2α release into the circulation. Greater release of PGF to the circulation in period 2 (addition of PGE₂) is probably the result of the vasodilatory effect of PGE₂ on uterine endometrial vasculature.     

Abortion after PGF2α in heifers with multiple pregnancies following superovulation with FSH and PGF2α

Multiple ovulations were induced with follicle stimulating hormone and estrus was synchronized with prostaglandin F_2α (PGF_2α) in 23 Holstein heifers. In 19 heifers which responded to the treatments, an average of 1.8 corpora lutea were formed after the induced estrus and 6 of 19 heifers conceived (total of ten fetuses at 39 days gestation) to artificial insemination at 60 and 84 hr after the PGF_2α injection. Injection of 33 mg PGF_2α Tham salt into the six pregnant heifers on day 40 of gestation caused abortion between 54 and 66 hr after treatment in all heifers.     

Prostaglandin F2α promotes ovulation in prepubertal heifers

The objective was to determine the effects of exogenous prostaglandin F_2α (PGF), with or without progesterone treatment, on first ovulation in prepubertal heifers. We tested the hypothesis that PGF has a luteolysis-independent ovulatory effect in cattle. Crossbred Angus heifers (12 to 14 mo old, 250 kg body weight, and an average body condition score of 3 out of 5) were examined by transrectal ultrasonography on two occasions, 11 days apart. Heifers in which a CL was not detected at either examination were considered prepubertal. Heifers were assigned randomly to three experimental groups: (1) PG group (N = 14); heifers were treated with a PGF analog (500 μg cloprostenol im) 5 days after the emergence of a spontaneous (i.e., naturally occurring, noninduced) follicular wave; (2) PPG group (N = 12); heifers were given an intravaginal progesterone-releasing insert (CIDR; Pfizer Animal Health, Montreal, QC, Canada), and a follicular wave was induced with 50 mg of progesterone + 2 mg of estradiol benzoate im, and a PGF analog was given at the time of CIDR removal, on Day 5 of the follicular wave (on average, 8.6 ± 0.5 days after CIDR insertion); and (3) control group heifers were given no treatment (N = 14). Heifers were examined daily by transrectal ultrasonography from the start of the experiment to confirmation that ovulation had occurred, or to 5 days after PGF injection (PG and PPG groups) or until dominant follicles of the next follicular wave reached 8 mm (control group). The percentage of heifers that ovulated within 10 days after wave emergence was higher in PPG (10/12; 83.3%) and PG (11/14; 78.5%) groups than in control (1/14; 7.1%; P < 0.0001). Ovulations occurred 69.6 ± 6 h and 93.8 ± 5 h after PGF treatment in PPG and in PG groups, respectively, whereas only one heifer in the control group ovulated 96 h after Day 5 of follicular wave (P = 0.13). In summary, PGF treatment was associated with ovulation in prepubertal heifers whether or not exogenous progesterone was used as a pretreatment. The hypothesis that PGF will induce ovulation by a luteolysis-independent mechanism was supported.     

Role of PGF2α in luteolysis based on inhibition of PGF2α synthesis in the mare

The effects of inhibition of PGF2α synthesis on luteolysis in mares and on the incidence of prolonged luteal activity were studied in controls and in a group treated with flunixin meglumine (FM), a PGF2α inhibitor (n = 6/group). The FM was given every 8 hours (1.0 mg/kg) on each of Days 14.0 to 16.7. Concentration (pg/mL) of PGF2α metabolite averaged over 8 hours of hourly blood sampling at the beginning of each day, was lower in the FM group than in the controls on Day 14 after ovulation (6.7 ± 1.3 vs. 13.8 ± 2.9, P < 0.05), Day 15 (15.0 ± 3.9 vs. 35.2 ± 10.4, P < 0.10), and Day 16 (21.9 ± 5.7 vs. 54.7 ± 11.4, P < 0.03). Concentration (ng/mL) of progesterone (P4) was greater in the FM group than in the controls on Day 14 (10.1 ± 0.9 vs. 7.7 ± 0.9, P < 0.08), Day 15 (9.2 ± 1.0 vs. 4.3 ± 1.0, P < 0.008), and Day 16 (5.6 ± 1.6 vs. 1.2 ± 0.4, P < 0.02). The interval from ovulation to the beginning of a decrease in P4 and to the end of luteolysis (P4 < 1 ng/mL) was each delayed (P < 0.03) by ∼1 day in the FM group. Intervals involving the luteal phase were long (statistical outliers, P < 0.05) in two mares in the FM group, indicating prolonged luteal activity. Results supported the hypotheses that (1) inhibition of PGF2α synthesis interferes with luteolysis in mares and (2) inhibition of PGF2α at the expected time of luteolysis may lead to prolonged luteal activity.     

Metabolites of PGF2α in Blood Plasma and Urine as Parameters of PGF2α Release in Cattle

The metabolism of PGF2α in cattle results initially in the formation of 15-keto-13,14-dihydro-PGF2α (15-ketodihydro-PGF2α) and later the 11-ketotetranor PGF metabolites. Both types of metabolites appear in the peripheral circulation and finally the 11-ketotetranor PGF metabolites are found in large quantities in the urine in a species-related pattern. Several approaches can be made to the quantitative analysis of PGF2α release during reproductive studies. First, assay of the 15-ketodihydro-PGF2α metabolite in the peripheral circulation; second, analysis of the longer-lived 11-ketotetranor PGF metabolites in the peripheral circulation; and finally analysis of the latter metabolites in the urine. The antibodies used in radioimmunoassays of both types of metabolites of PGF2α were found to be specific and the results agree well with those obtained earlier by mass spectrometric analysis. The assay of 11-ketotetranor PGF metabolites was used to study the excretion of urinary metabolites in the cow after i.v. infusion of PGF2α and also during the normal estrous cycle and early pregnancy. These studies suggest that 11-ketotetranor PGF metabolites in cow urine serve as a good parameter of PGF2α release, especially for long–term studies, but when a precise pattern of PGF2α release is required, measurement of 15-ketodihydro-PGF2α levels in frequently collected plasma samples is preferable.     

Prostaglandin F2α-induced stimulation of estrone and estradiol-17β secretion in cattle

Four of 5 Holstein heifers given intra-ovarian injections of 300 μg of prostaglandin F_2α (PGF_2α) showed transient, but statistically significant, depressions in plasma progesterone levels which returned to near normal levels within 24 hr. The same 4 animals also exhibited significant elevations in plasma estrone and estradiol-17β levels during the initial 24 hr. period following treatment, although no animals were observed in estrus during this time. Plasma levels of progesterone, estrone, estradiol-17β and PGF showed little change in control heifers receiving intra-ovarian injections of the buffer solution used as a vehicle for PGF_2α. It is concluded that PGF_2α stimulates estrogen secretion, presumably by follicular elements of the ovary.     

Exogenous Prostaglandin F2α Promotes Uterine Involution in the Cow

Three newly delivered dairy cows were given prostaglandin F2α during the immediate postpartum period. PGF2α was administered from day 3–13 post partum in doses of 25 mg twice daily. Endogenous release of PGF2α and progesterone was studied in blood plasma during the experimental period. Rectal examination of the uterus was performed every second day in order to establish the end of uterine involution. Uterine involution in the three cows was completed days 16, 23 and 20, respectively. These figures are to be compared with earlier investigations of uterine involution times, which show about 27 days. It was concluded that PGF2α had a positive effect on the uterine muscular tone.     

Prostaglandin F2α Concentrations in Peripheral Blood During the First Stage of Normal Labour

Plasma prostaglandin F₂α (PGF₂α) concentrations were measured by radioimmunoassay in women in normal first stage labour. A continuous sampling technique was used spanning uterine contractions, and blood samples were divided into 15-second aliquots.A regular pattern of rise in prostaglandin levels in peripheral plasma was observed, with maximum concentrations in the antecubital vein being reached in most cases 15-45 seconds after the peak of a uterine contraction. The most likely explanation of this finding is that prostaglandins are released as a result of uterine contractions. The alternative possibility is that prostaglandins initiate uterine contractions. Further studies of the time taken for blood to reach the antecubital vein are needed to clarify the position.     

Clinical Relevance of Plasma Prostaglandin F2α Metabolite Concentrations in Patients with Idiopathic Pulmonary Fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease of unknown etiology with few current treatment options. Recently, we determined an important role of prostaglandin F_2α (PGF_2α) in pulmonary fibrosis by using a bleomycin-induced pulmonary fibrosis model and found an abundance of PGF_2α in bronchoalveolar lavage fluid of IPF patients. We investigated the role of PGF_2α in human IPF by assessing plasma concentrations of 15-keto-dihydro PGF_2α, a stable metabolite of PGF_2α.

Methods

We measured plasma concentrations of 15-keto-dihydro PGF_2α in 91 IPF patients and compared these values with those of controls (n = 25). We further investigated the relationships of plasma 15-keto-dihydro PGF_2α concentrations with disease severity and mortality.

Results

Plasma concentrations of 15-keto-dihydro PGF_2α were significantly higher in IPF patients than controls (p<0.001). Plasma concentrations of this metabolite were significantly correlated with forced expiratory volume in 1 second (Rs [correlation coefficient] = −0.34, p = 0.004), forced vital capacity (Rs = −0.33, p = 0.005), diffusing capacity for carbon monoxide (Rs = −0.36, p = 0.003), the composite physiologic index (Rs = 0.40, p = 0.001), 6-minute walk distance (Rs = −0.24, p = 0.04) and end-exercise oxygen saturation (Rs = −0.25, p = 0.04) when patients with emphysema were excluded. Multivariate analysis using stepwise Cox proportional hazards model showed that a higher composite physiologic index (relative risk = 1.049, p = 0.002) and plasma 15-keto-dihydro PGF_2α concentrations (relative risk = 1.005, p = 0.002) were independently associated with an increased risk of mortality.

Conclusions

We demonstrated significant associations of plasma concentrations of PGF_2α metabolites with disease severity and prognosis, which support a potential pathogenic role for PGF_2α in human IPF.     

Combination of the ram effect with PGF2α estrous synchronization treatments in ewes during the breeding season

The role of the ram effect on the reproductive performance of ewes that have initiated estrous cycles following lambing in combination with synchronization of estrus using PGF(2α) was examined. A total of 1264 Corriedale × Merino ewes in the breeding season (March-April) were allocated to one of three treatments. The control group (PG2) of ewes (n=415) were in permanent direct contact with vasectomized rams throughout the experiment from 60 d prior to the administration of the first luteolytic dose of PGF(2α) which was followed by a second dose 13 d later (Day 0 of the experiment). Ewes assigned to the other two treatments remained isolated from rams until Day 0. In the second treatment, ewes (PG2RE; n=445) were administered PGF(2α) in the same manner and were joined with vasectomized rams at Day 0. Ewes allocated to the third treatment (PGRE; n=404) did not receive the second dose of PGF(2α) but were introduced to vasectomized rams on Day 0. Sexual receptivity, as indicated by tail-head marking, was recorded until d 11. More PG2RE ewes (407/445; 92%) were observed in estrus by Day 11 than occurred for PG2 ewes (353/415; 85%; P=0.003). The accumulated frequency of PG2RE ewes in estrus was greater than for PG2 ewes for each period from Day 3 (P<0.001) to Day 11 (P<0.01). The onset of estrus was earlier in PG2RE ewes (2.98±0.07 d) than for PG2 ewes (3.31±0.07 d; P<0.0001). In contrast, the total frequency of PGRE ewes observed in estrus by Day 11 (356/404; 88%) was similar to that observed for PG2 ewes. However, the trajectory of the accumulated frequency of the incidence of estrus was less for the PGRE ewes initially, particularly during the period of Days 3-6 of observation (P<0.0001). Consequently, onset of estrus was earlier in PG2 ewes (3.31±0.07 d) than for PGRE ewes (5.30±0.11 d; P<0.0001). It was concluded that the introduction of vasectomized rams simultaneously with the second administration of PGF(2α) advanced the onset of estrus and increased the number of ewes that responded. The introduction of rams 13 d after a single dose of PGF(2α) did not substitute for the second administration of PGF(2α).     

Use of the prostaglandin F2α analog cloprostenol (ICI 80, 996) in dairy cattle with unobserved estrus

Two field trials were designed to evaluate use of the prostaglandin F_2α analog cloprostenol (CP) in dairy cattle with unobserved estrus and a palpably mature corpus luteum (CL). In Trial 1, 98 cows were treated with CP (500 μg IM) and 83 were given saline. Cows in both groups were assigned to be inseminated based on observed signs of estrus. Cows treated with CP were inseminated sooner than controls although heat detection still presented some difficulty. Conception rates were the same for both groups. In Trial 2, 154 cows were treated with CP for unobserved estrus and were assigned to be inseminated at estrus (78 cows) or were inseminated twice by appointment at 72 and 96 hours after treatment (76 cows). Appointment breeding eliminated problems associated with detection of estrus so nearly all cows were inseminated soon after treatment. In addition, cows bred twice by appointment had a higher conception rate than those bred based on signs of estrus. Induction of luteolysis with the prostaglandin F_2α analog CP in cows with unobserved estrus and a CL should prove to be a very effective addition to reproductive herd health programs. Successful use of CP for this purpose is dependent upon accurate diagnosis of the presence of a mature CL. In these trials 83 (92.4%) of 90 cows sampled had blood serum progesterone concentrations indicative (≥ 2.0 ng/ml) of significant luteal tissue activity.     

Doses of prostaglandin F2α effective for induction of parturition in goats

Twelve mixed breed does were injected with different doses of prostaglandin F₂α (PGF₂α) or saline on day 144 of gestation. Four each received single intramuscular injections of 5.0 or 2.5 mg PGF_2α, or 1.0 ml saline (controls). Systemic progesterone (P₄) concentrations were determined daily from day 144 until the day of kidding. Does receiving 5.0 mg PGF₂α, 2.5 mg PGF₂α, or saline kidded within mean (± SD) hours and range (hours) of 35 ± 8.6 and 28–48, 43 ± 11.8 and 29–57, and 111 ± 79.1 and 41–200, respectively. Mean (± SD) concentrations of P₄ (ng/ml) on the day of injection and on day 1 postinjection were 5.2 ± 2.6 and 0.7 ± 0.9, 5.3 ± 2.2 and 1.1 ± 1.0, and 6.4 ± 3.9 and 4.1 ± 2.6 for does receiving 5.0 mg PGF₂α, 2.5 mg PGF₂α, or saline, respectively. It was concluded that 5.0 mg and 2.5 mg PGF₂α effectively shortened the interval from injection to parturition, but that this interval was not as predictable as that previously reported with 20 mg PGF₂α.     

Pyometra in Bitches Induces Elevated Plasma Endotoxin and Prostaglandin F2α Metabolite Levels

   

Endotoxemia in bitches with pyometra can cause severe systemic effects directly or via the release of inflammatory mediators. Plasma endotoxin concentrations were measured in ten bitches suffering from pyometra with moderately to severely deteriorated general condition, and in nine bitches admitted to surgery for non-infectious reasons. Endotoxin samples were taken on five occasions before, during and after surgery. In addition, urine and uterine bacteriology was performed and hematological, blood biochemical parameters, prostaglandin F_2α metabolite 15-ketodihydro-PGF_2α (PG-metabolite), progesterone and oestradiol (E₂-17β) levels were analysed.     

The effect of a single high dose of PGF2α administered to dairy cattle 3.5 days after ovulation on luteal function,morphology, and follicular dynamics

A single treatment with PGF2α is assumed to have no luteolytic effect on cows with corpora lutea < 5 days old. The objective of this study was to determine the effect of a single high dose of PGF2α administered to dairy cattle on the morphology and function of the early CL. The study followed a crossover design with a treatment cycle in which 50 mg of dinoprost were administered 3.5 days postovulation and a control untreated cycle. Ultrasound examination and blood samples were performed during the two consecutive cycles. Corpus luteum (CL) diameter, progesterone concentration, and follicular dynamics characteristics were compared between control and treated cycles. Two of nine cows (22%) developed full luteolysis. The remaining seven cows (78%) had partial luteolysis with a decrease (P < 0.05) in progesterone concentration and CL diameter for two and 12 days post-treatment, respectively. The interovulatory interval of treated cycles (19.7 ± 2.4 days) was not different (P > 0.05) from that of controls (23.8 ± 0.9 days). The transient reduction in progesterone of cows with partial luteolysis had no effect on the proportion of cows with two or three follicular waves, follicle growth rate, or preovulatory diameter (P > 0.05). Two cows developed ovarian cystic degeneration during the PGF2α-induced cycle. In conclusion, the treatment of cows with a high dose of PGF2α 3.5 days postovulation induced some degree of luteolysis in all treated cows. This resulted in partial luteolysis in 78% of treated animals and in full luteolysis in the remaining 22%.     

Detection of estrous behavior in buffalo heifers by radiotelemetry following PGF2α administration during the early or late luteal phase

This study examined the usefulness of radiotelemetry for estrous detection in buffalo heifers and the impact of prostaglandin F_2α (PGF_2α) administration during the early or late luteal phase on estrous behavior and ovulatory follicle variables. Induction of estrus with PGF_2α at a random stage of the estrous cycle was followed by the arbitrary division of heifers into groups receiving a second dose of PGF_2α during either the early (n = 33) or late (n = 17) luteal phase (6–9 or 11–14 days after estrus, respectively) for the induction of synchronized estrus. The electronic detection of synchronized estrus by radiotelemetry was confirmed using ultrasonography every 6 h until ovulation. Radiotelemetry was 90% efficient and 100% accurate for estrous detection. Intervals between the PGF_2α dose and the beginning of synchronized estrus (40.7 ± 10.9 vs. 56.7 ± 12.8 h) or ovulation (70.0 ± 11.3 vs. 85.6 ± 12.5 h) were shorter (P < 0.05) for heifers receiving PGF_2α during the early luteal phase. PGF_2α administration during the early or late luteal phase produced similar (P > 0.05) results for the duration of estrus, the intervals from the beginning or end of estrus to ovulation, the number and duration of mounts per estrus, the duration of mounts, the diameter of the ovulatory follicle and the luteal profile on day 5 after estrus. In conclusion, radiotelemetry was a suitable tool for the efficient and accurate detection of estrus in buffalo heifers. Treatment with PGF_2α during the early luteal phase had a shorter interval to synchronized estrus and ovulation; however, estrous behavior, ovulatory follicle dynamics and subsequent luteal activity were similar following PGF_2α administration during the early or late luteal phase.