Effect Of Prostaglandin F2α Research Articles

Prostaglandin F2α treatment does not hasten ovulation in weaned sows

This study evaluated the efficiency of prostaglandin F2α (PGF) to hasten ovulation in weaned sows. In experiment I, weaned sows detected in estrus (0 h) received: no hormone (Control; n = 56); 0.5 mg PGF IM at 0 h and 2 h (PGF0; n = 56); or 0.5 mg PGF IM at 24 h and 26 h (PGF24; n = 55). In experiment II, weaned sows that did not express estrus signs until 72 h after weaning (0 h) were assigned to: no hormone (Control; n = 45); 10 µg buserelin acetate IM at 0 h (Buserelin; n = 43); 0.5 mg PGF IM at 34 h and 36 h (PGF; n = 44); or 10 µg buserelin acetate IM at 0 h plus 0.5 mg PGF IM at 34 h and 36 h (Buserelin + PGF; n = 45). In experiment I, no effect of PGF on the interval treatment onset to ovulation was observed (P > 0.05), and no treatment effect was observed on the relative or cumulative proportion of females that ovulated post-treatment onset (P > 0.05). In experiment II, treatment onset to ovulation interval was shorter for Buserelin group than for PGF group (P < 0.05), and a higher cumulative percentage of Buserelin treated sows ovulated up to 48 h compared to PGF and Control groups (P < 0.01), with no differences from Buserelin + PGF. Treatments did not affect total number of piglets born in both experiments (P > 0.05). In conclusion, PGF did not hasten ovulation timing or affect litter size in weaned sows.

Prostaglandin F2α Causes Fast Degenerative Changes in Ovulated Mouse Oocytes

The effects of prostaglandin F2α on the cytoskeleton and membrane organelles of oocytes was investigated by culturing ovulated mouse oocytes in its presence (50 or 100 ng/ml) for 3 h. Tubulin, fibrillar actin, membranes and chromatin were visualized by specific antibodies, phalloidin, lipophilic dye DiOC6 and Hoechst 33342, respectively. Control oocytes were characterized by a meiotic spindle with chromosomes aligned at its equator, and a cortical layer of microfilaments with an actin cap. Intracellular membranes were localized mostly in the central region in metaphase I and in a broader volume, but still excluding the cell periphery, in metaphase II, and were slightly concentrated around the chromosomes. In oocytes treated with 50 ng/ml prostaglandin, cortical actin staining was diminished, the membrane distribution was clustered, and chromosomes showed signs of misalignment despite the apparently preserved spindle. In cells treated with 100 ng/ml prostaglandin, both the spindle and the actin cortex had degenerated or disappeared as microscopic objects. Metaphase plates were on average broader and more disorganized than in the 50 ng/ml group, and the distribution of membrane organelles had become uniform. These effects, to our knowledge observed for the first time, did not require presence of the cumulus during the incubation. They could be regarded as acceleration of the oocyte postovulatory aging, in which cytoskeletal deterioration seemed to have a leading role.

Effects of prostaglandin F2α on angiogenic and steroidogenic pathways in the bovine corpus luteum may depend on its route of administration

Prostaglandin (PG) F2α and its analogs (aPGF2α) are used to induce regression of the corpus luteum (CL); their administration during the middle stage of the estrous cycle causes luteolysis in cattle. However, the bovine CL is resistant to the luteolytic actions of aPGF2α in the early stage of the estrous cycle. The mechanisms underlying this differential luteal sensitivity, as well as acquisition of luteolytic sensitivity by the CL, are still not fully understood. Therefore, to characterize possible differences in response to aPGF2α administration, we aimed to determine changes in expression of genes related to (1) angiogenesis-fibroblast growth factor 2 (FGF2), fibroblast growth factor receptor 1 (FGFR1), fibroblast growth factor receptor 2 (FGFR2), vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor receptor 1 (VEGFR1), vascular endothelial growth factor receptor 2 (VEGFR2); and (2) steroidogenesis-steroidogenic acute regulatory protein (STAR), cytochrome P450 family 11 subfamily A member 1 (P450scc), and hydroxy-delta-5-steroid dehydrogenase, 3 β- and steroid delta-isomerase 1 (HSD3B) in early- and middle-stage CL that accompany local (intra-CL) versus systemic (i.m.) aPGF2α injection. Cows at d 4 (early stage) or d 10 (middle stage) of the estrous cycle were treated as follows: (1) systemic saline injection, (2) systemic aPGF2α injection (25 mg), (3) local saline injection, and (4) local aPGF2α injection (2.5 mg). Progesterone (P4) concentration was measured in jugular vein blood samples during the entire set of experiments. After 4 h of treatment, CL were collected by ovariectomy, and mRNA and protein expression levels were determined by reverse transcription quantitative-PCR and Western blotting, respectively. Local and systemic aPGF2α injections upregulated FGF2 expression but decreased expression of VEGFA in both CL stages. Both aPGF2α injections increased the expression of STAR in early-stage CL, but downregulated it in middle-stage CL. In the early-stage CL, local administration of aPGF2α upregulated HSD3B, whereas systemic injection decreased its mRNA expression in early- and middle-stage CL. Moreover, we observed a decrease in the P4 level earlier after local aPGF2α injection than after systemic administration. These results indicate that aPGF2α acting locally may play a luteotrophic role in early-stage CL. The systemic effect of aPGF2α on the mRNA expression of genes participating in steroidogenesis seems to be more substantial than its local effect in middle-stage CL.

Effect of prostaglandin F2α and GnRH administration at the time of artificial insemination on reproductive performance of dairy cows.

The present study aimed to determine the effect of administrating prostaglandin F2α (PGF2α) and GnRH at the time of artificial insemination (AI) on the pregnancy per artificial insemination (P/AI) and the pregnancy survival rate of dairy cows. A number of 830 lactating Holstein cows were randomly divided into four groups. Cows in group 1 (n=200) treated with 150 µg d-cloprostenol. In group 2 (n=212), cows received 10 µg buserelin acetate, and group 3 (n=205) was treated with both 150 µg d-cloprostenol and 10 µg buserelin acetate. In addition, 213 cows were assigned as control group which received normal saline as placebo (group 4). To measure progesterone, milk samples were collected at the insemination day and five days later. Pregnancy diagnosis was performed 28 and 60 days after the insemination, and the size and number of corpus luteum (CL) and twin pregnancies were recorded. Hormone therapies had no effect on the P/AI, pregnancy survival rate, and the size and number of CL. The P/AI ratio in groups 1, 2, 3 and 4 were 38.50%, 42.92%, 41.46% and 40.84%, and the pregnancy survival rates in groups 1, 2, 3 and 4 were 84.42%, 86.81%, 88.23% and 83.91%, respectively. The probability of a twin pregnancy was significantly higher in group 1 (15.58%) than other groups. There was no significant difference between groups in terms of the offspring gender. In conclusion, the administration of d-cloprostenol or buserelin acetate at the time of AI had no effect on P/AI and pregnancy survival rate in dairy cattle under no heat stress condition, while the administration of d-cloprostenol increased the probability of twin pregnancies.

Effect of Prostaglandin F2α on Estrus Synchronization in Crossbred and Indigenous Cows on Smallholder Dairy Farms in Mazabuka, Zambia

Effect of Prostaglandin F2α on Estrus Synchronization in Crossbred and Indigenous Cows on Smallholder Dairy Farms in Mazabuka, Zambia

Precision-cut luteal slices: A promising approach for studying luteal function in pigs

The study was aimed to validate the precision-cut luteal slices to investigate porcine luteal function. Corpora lutea (CLs) were cut into 180-μm thick slices using Krumdick Tissue Slicer. The viability, tissue structure and steroidogenic acute regulatory protein (STAR) expression in the luteal slices did not differ between the beginning and the end of the 24-h incubation period. The luteal progesterone secretion showed a time- and dose-dependent response to porcine luteinizing hormone. The effects of prostaglandin F2α and 17β-estradiol on progesterone secretion by porcine luteal slices were comparable to the previously reported in vivo results of the CL microdialysis system in the pig.

Effect of Prostaglandin F2α on Growth of Staphylococcus Aureus Associated with Bovine Mastitis

Staphylococcus aureus is a major infectious organism causing mastitis. Certain fatty acids have been shown to inhibit the growth of pathogens including Staphylococcus aureus. An in vitro experiment was conducted to determine the effects of prostaglandin F2α (PGF2α) on growth of S. aureus. Flasks containing tryptic soy broth (TSB) were inoculated with S. aureus Novel, and subsequently treated with PGF 2α (dinoprost tromethamine) at concentrations of 0, 0.3, 0.6, 1.2, and 2.4 mg/ml. Cultures were incubated at 37°C for 24 h and sampled every 3 h. The entire experiment was conducted three times in duplicates. Bacterial growth was assessed by counting colony forming units (CFU) in triplicates. Data were analyzed by repeated measures analysis of variance and reduced and full dummy variable regression models to determine the effect of PGF2α concentrations on growth patterns of S. aureus over time. There was an effect of treatment and treatment by time interaction (P<0.05) on mean log CFU, indicating that bacterial growth over 24 h was different across treatments. At time of inoculation (0 h), mean log CFU values were not different among treatments; however at 24 h, mean log CFU for each PGF 2α treatment was different from control and decreased (P<0.05) with increasing concentrations of PGF 2α . The predicted growth curve for each treatment was different (P<0.05) when compared with the control, and the rate of bacterial growth was less for 1.2 mg/ml PGF 2α when compared with the control and 0.6 mg/ml. The bacterial growth was completely inhibited during the 24 h period in 2.4 mg/ml PGF 2α treatment. Furthermore, a non-linear regression model was employed to estimate the dose response at the 24 h, and revealed that 1.2 mg/ml was the minimum inhibitory dose. These results provide evidence, for the first time, that PGF 2α , in the form of dinoprost tromethamine, has bacteriostatic and bactericidal effects on S. aureus in vitro.

Effect of prostaglandin F2α on uterine contractile activity and hormonal and biochemical status of cows

The stimulating effect of PGF2α on uterine contractile function of cows after calving and reaction of endocrine, bioenergetic, and amino acid systems and nitrogen oxide system to its injection are determined. The current notion about the molecular and biochemical mechanisms of the effect of prostaglandins on processes of postpartum involution of genital organs is broadened.

Effect of prostaglandin F2α on subclinical endometritis and fertility in dairy cows

The objectives were to determine the effects of PGF2α treatment on the prevalence of subclinical endometritis (SCE) and fertility of dairy cows. A total of 406 Holstein cows (167 primiparous and 239 multiparous) from 5 herds were used. Uterine lavage for diagnosis of SCE, PGF2α treatment, evaluation of body condition scores (BCS), and collection of blood samples for estrous cyclicity determination were performed at 21, 35, and 49 d in milk (DIM). Polymorphonuclear cells (PMN) were quantified and thresholds for diagnosing SCE were selected by receiver operating characteristics analysis. Cows classified as having SCE at 35 DIM (≥6.5% PMN) and 49 DIM (≥4.0% PMN) had increased time to pregnancy; however, cows classified as having SCE at 21 DIM (≥8.5% PMN) did not. Median days to pregnancy were delayed by 30 (151 vs. 121 d) and 40 (169 vs. 129) d for cows classified as having SCE at 35 and 49 DIM, respectively. Treatment with PGF2α did not affect the prevalence of SCE either at 35 (37.9 vs. 38.4%) or at 49 DIM (34.0 vs. 40.4%). Treatment with PGF2α did not affect time to first insemination (AI; median 76 DIM for cows treated with PGF2α; 79 DIM for control. Nonetheless, PGF2α treatment increased pregnancy to first AI in all the cows (35.5 vs. 24.1%) and hazard ratio (HR) of pregnancy in cows with BCS ≤2.5 when all of the cows were evaluated (HR = 1.5; 95% confidence interval; CI = 1.1 to 2.0) and when only cows without SCE were evaluated (HR = 1.8; 95% CI = 1.2 to 2.7). Treatment with PGF2α did not affect the hazard of pregnancy in cows with SCE at 49 DIM (HR = 0.9; 95% CI = 0.6 to 1.3). In these farms, treatment with PGF2α did not affect SCE or time to first insemination, but did increase first-service pregnancy per AI and decreased time to pregnancy in cows with low BCS.

147 A PROSTAGLANDIN F2Alpha RECEPTOR ANTAGONIST MAY INHIBIT BAX EXPRESSION IN BOVINE PRE-IMPLANTATION EMBRYOS DURING EMBRYO FLUSHING

Several in vivo studies have shown negative effects of prostaglandin F2α (PGF2α) on embryonic survival in cows. The PGF2α receptor (FPr) was detected in bovine embryos (Scenna FN et al. 2006 Reprod. Fertil. Dev. 18, 180). Recently, it was reported that addition of a FPr antagonist (AL-8810) to the embryo flushing medium prevented the detrimental action of PGF2α on pregnancy (Scenna FN et al. 2008 Reprod. Fertil. Dev. 20, 154). In the present study, we examined the morphological development in utero and gene expression of bovine pre-implantation embryos collected using flushing medium containing AL-8810. Embryos were collected from superovulated donors on Day 7 after artificial insemination with medium containing 1000 nm AL-8810 (n = 4, Sigma-Aldrich, St, Louis, MO, AL embryos) or with vehicle (n = 4, DMSO, Sigma-Aldrich, CON embryos). Following collection, the embryos were classified by quality and stage, and then 2 to 5 grade-1, stage 4 and 5 embryos (IETS classification) were transferred to recipient heifers (AL-embryos: n = 4, CON embryos: n = 4) for transient development in utero up to Day 15 of gestation. Embryos at Day 15 occasionally collapsed after uterine flushing due to breaches in trophectoderm (TE) tissue caused by the collection procedures. Only whole embryos were used and evaluated in this study. Using real-time PCR, the TE cells were examined to quantify the mRNA levels for 3 genes, interferon-τ (maternal recognition of pregnancy, INF-τ), connexin 43 (cell communication, CX 43) and Bcl-2-associated X protein (apoptosis, Bax). Data were analyzed using Student’s t-test and chi-square test. The average number of ova/embryos recovered at Day 7 was 12.0 ± 4.1 (AL embryos) and 8.8 ± 5.8 (CON embryos). There was no significance in the percentages of transferable embryos (AL-embryos; 67.0 ± 14.4%, 35/48 and CON-embryos; 79.6 ± 7.1%, 27/35; P &gt; 0.05) between the 2 groups. The whole-embryo recovery rate on Day 15 for AL embryos (73.3%, 11/15) was &gt;30 percentage points greater than that for CON embryos (41.2%, 7/17). The length of major axis of embryos and the diameter of embryonic disks were the same between AL embryos (59.6 ± 12.3 mm, 0.44 ± 0.03 mm, respectively) and CON embryos (49.3 ± 24.6 mm, 0.43 ± 0.05 mm, respectively). Transcripts of INF-τ and CX 43 in TE cells did not differ significantly between AL embryos and CON embryos (P &gt; 0.05). However, the abundance of Bax transcripts in TE cells tended to be lower in AL embryos than in CON embryos (P = 0.07). These results suggest that addition of an FPr antagonist to the embryo flushing medium may promote the developmental capacity of pre-implantation embryos in utero.

Effect of Prostaglandin F2α (PGF2α) Administration on the Luteotropic and Angiogenic Factors During Functional Luteolysis in the Bovine Corpus Luteum.

The essential role of endometrium PGF2α in induction of the corpus luteum (CL) regression (luteolysis) is well documented in the cow. However, the following regulatory cascade of functional luteolysis is still not fully elucidated. The aim of the present study was therefore to determine the regulation patterns of local luteotropic factors (progesterone, oxytocin and insulin-like growth factor (IGF) family members) and angiogenic factors (vascular endothelial growth factor-A (VEGF) and angiopoietin (ANPT) family members) during functional luteolysis (first 12 h after PGF2α injection) in time-defined CL classes. Cows (n=4-5 per group) in the mid-luteal phase (days 8-12) were injected with the PGF2α-analogue (cloprostenol), and CLs were collected by transvaginal ovariectomy at 0 h, 0.5 h, 2 h, 4 h and 12 h after PGF2α injection. The mRNA expression was analyzed by a quantitative real-time PCR (Rotor-Gene 3000), and the protein concentration was evaluated by enzyme immunoassay (EIA) or radio immunoassay (RIA). Progesterone concentration in blood serum and in CL tissue as well as mRNA expression of progesterone receptor in CL tissue, were significantly downregulated at 12 h after PGF2α. Oxytocin and IGF-1 peptide concentrations rapidly declined after 0.5 h and remained at low level afterwards. The IGF binding protein (BP)-1 mRNA was strongly upregulated with the maximal level at 4 h after PGF2α. This may cause further reduction of bioactive free IGF-1 in tissue. The VEGF protein decreased also at 0.5 h, with a synchronous acute and temporal increase of angiopoietin (ANPT)-2 peptide concentrations (0.5 h and 2 h after PGF2α). The similar tendency of upregulation of ANPT-2 was found for mRNA expression level, whereas the level of ANPT-1 mRNA did not change. The results suggest that the acute decrease of the local luteotropic factors and of VEGF may play a key role during the early step of functional luteolysis. The increase of ANPT-2 after PGF2α suggests a change in vascular stability to enhance the cascade of functional luteolysis.

Effect of prostaglandin F2α at the time of AI on progesterone levels and pregnancy rate in synchronized Italian Mediterranean buffaloes

The aims of this study were to evaluate the effects of an intravenous or intramuscular PGF2alpha analogue administration on the day of estrus on progesterone concentration and pregnancy rate in buffaloes undergoing artificial insemination (AI). To this end, two experiments were carried out. The first study was performed on 72 Mediterranean buffaloes synchronized by the Ovsynch-TAI Program. On the day of estrus only animals considered in heat were divided into four groups: Groups IVC and IMC received, respectively, an intravenous or intramuscular injection of cloprostenol (0.524 mg), whereas control Groups IVS and IMS received the same injections of saline. Milk samples were collected daily from each animal to assess progesterone concentration in the whey by RIA method. In addition on alternate days, buffaloes underwent transrectal ultrasound analysis. The second study was carried out on 385 buffaloes synchronized by the Ovsynch-TAI Program. On the day of AI, animals were divided in four groups, as described in experiment 1. Pregnancy rate was evaluated either on day 26 or day 45 and embryonic mortality rate was recorded. Statistical analysis was performed by ANOVA and chi2 test. A higher (P<0.05) progesterone concentration was recorded on day 11 (Day 0=estrus day) in Groups IVC and IMC compared to Groups IVS and IMS (351.6+/-129.7 and 355.8+/-112.2 pg ml(-1) vs. 239.8+/-81.1 and 243.6+/-90.5 pg ml(-1), respectively). Furthermore, a larger CL was recorded on the same day in treated vs. control groups (1.25+/-0.15 and 1.27+/-0.17 cm, respectively, in Groups IVC and IMC vs. 1.08+/-0.14 and 1.05+/-0.13 cm in IVS and IMS). In the second study, a higher pregnancy rate was observed in treated (IVC+IMC) vs. control (IVS+IMS) groups (46.7% vs. 30.7%; P<0.01), while no differences were recorded between treated groups. From these data, it can be concluded that either intravenous or intramuscular administration of PGF2alpha at the time of AI can enhance progesterone levels and pregnancy rate in buffaloes.

146 DETRIMENTAL EFFECTS OF PROSTAGLANDIN F2α ON IN VITRO EMBRYO DEVELOPMENT IN BOVINE ARE INHIBITED BY A RECEPTOR ANTAGONIST

Numerous studies have demonstrated negative effects of prostaglandin F2α (PGF2α) on bovine reproduction. Discovery of a PGF2α receptor (FPr) in bovine embryos (Scenna et al. 2006 Reprod. Fertil. Dev. 18, 180) allows for development of new therapeutic strategies to improve success of embryo transfer. Therefore, two experiments were performed to investigate the occurrence of any toxic effect of AL-8810 (Cayman Chemical Inc., Ann Arbor, MI, USA), an FPr antagonist, on in vitro development of bovine embryos. In Exp. 1, pre-compacted embryos were cultured in (1) 100 AL (100 nm AL-8810 in potassium simplex optimized medium with polyvinyl alcohol (KSOM-PVA); n = 94); (2) 50 AL (50 nm AL-8810 in KSOM-PVA; n = 94); (3) 25 AL (25 nm AL-8810 in KSOM-PVA; n = 94); and (4) CON (control: KSOM-PVA; n = 95). In Exp. 2, pre-compacted embryos were cultured in (1) 1000 AL (1000 nm AL-8810 in KSOM-PVA; n = 282); (2) 500 AL (500 nm AL-8810 in KSOM-PVA; n = 274); (3) 250 AL (250 nm AL-8810 in KSOM-PVA; n = 274); and (4) CON (control: KSOM-PVA; n = 278). Embryos remained in treatments until blastocyst assessment. Next, two experiments were performed to determine the efficiency of AL-8810 on preventing detrimental effects of PGF2α on pre-compacted embryos. In Exp. 3, pre-compacted embryos were cultured in (1) 100 AL (100 nm AL-8810 in KSOM-PVA; n = 121); (2) 10 PGF (10 ng mL–1 of PGF2α (Cayman Chemical Inc.) in KSOM-PVA; n = 91); (3) AL100+PGF (100 nm AL-8810 and 10 ng mL–1 of PGF2� in KSOM-PVA; n = 116); (4) CON (control: KSOM-PVA; n = 96). In Exp. 4, embryos were cultured in (1) 1000 AL (1000 nm AL-8810 in KSOM-PVA; n = 87); (2) 10 PGF (10 ng mL–1 of PGF2α in KSOM-PVA; n = 87); (3) AL1000+PGF (1000 nm AL-8810 and 10 ng mL–1 of PGF2α in KSOM-PVA; n = 84); (4) CON (control: KSOM-PVA; n = 84). In Exp. 3 and 4, embryos remained in treatments for 48 h when development to morula was assessed. Data for all experiments were analyzed using the GLIMMIX procedure of SAS (SAS Institute, Inc., Cary, NC, USA). For Exp. 1, results indicated that addition of 100, 50, and 25 nm did not compromise embryonic development to the blastocyst stage compared to controls (60.2%, 55.8%, 55.4%, and 49.9%, respectively). In addition, orthogonal contrasts indicated that 100 nm AL-8810 improved development to the blastocyst stage (100 AL = 61% v. CON = 50.6%, P = 0.01). Similarly for Exp. 2, 1000, 500, and 250 nm AL-8810 did not affect in vitro development to the blastocyst stage compared to controls (40%, 39%, 34.8%, and 37.7%, respectively). In Exp. 3 and 4, addition of 1000 nm AL-8810, but not 100 nm, to culture medium of pre-compacted embryos exposed to PGF2α increased the ability of embryos to undergo compaction 48 h later (1000 AL+PGF = 51% v. PGF = 40%; P = 0.05). In conclusion, AL-8810 at a concentration of 1000 nm inhibits detrimental effects of PGF2α on the development of pre-compacted bovine embryos and may prove beneficial for other assisted reproductive techniques in cattle. Funding was provided by Ultimate Genetics and the Tennessee Agricultural Experiment Station for completion of these studies.

Effect of prostaglandin F2α on ovarian, adrenal, and pituitary hormones and on luteal blood flow in mares

The effect of a single injection of prostaglandin F2α (PGF) during mid-diestrus on systemic concentrations of progesterone, LH, FSH, estradiol, and cortisol and on blood flow to the corpus luteum was studied in 10 controls and 10 PGF-treated mares. Blood flow was assessed by estimating the percentage of corpus luteum with color-Doppler signals of blood flow during real-time scanning of the entire structure and by the diameter of the vascular pedicle near its attachment to the ovary. Treatment was done 8 days after ovulation and 0 h was immediately before the treatment. Examinations and collection of blood samples were done at 0 h, every 5 min until 1 h, and then at 1.5, 2, 4, 8, 12, 24, 48, and 72 h. The concentrations of estradiol did not change, but progesterone, LH, FSH, and cortisol increased significantly within 5 min. Concentrations of LH and FSH in the PGF group remained elevated until a temporarily lower concentration at 8 or 4 h, respectively, rebounded to 12 h, and then slowly decreased. Cortisol remained elevated, until a decrease between 1 and 4 h. Progesterone in the PGF group increased significantly until 10 min after 0 h and then decreased by 40 min to below the concentrations in controls. Within the PGF group, progesterone decreased significantly by 45 min to below the concentrations at 0 h. The values for each of the two indicators of blood flow did not differ significantly between the PGF and control groups until a decrease at 24 h in the PGF group. Results did not support the hypothesis that the immediate transient post-PGF increase in progesterone was associated with an increase in luteal blood flow. Luteolysis, as indicated by decreasing progesterone, began well before the beginning of a decrease in luteal blood flow.

Prostaglandin F2$alpha;-induced estrus in ewes exhibiting estrous cycles of different duration

Effects of prostaglandin F2α (PGF2α), administered during the mid-luteal phase of the estrous cycle, were examined in ewes exhibiting estrous cycles classified as short (≤16.5 days, short-cycle ewes, n=10) or long (≥18 days, long-cycle ewes, n=9) based on the durations of two estrous cycles (cycles −2 and −1) before treatment. The ewes received (i.m.) 20 mg of PGF2α on day 10 of the third estrous cycle (cycle 0) followed, 36 h later, by 25 μg of gonadotropin releasing hormone (GnRH) to time the events of ovulation. Duration of subsequent estrous cycles +1 and +2 were recorded, and then the ewes were treated with the same combination of PGF2α and GnRH beginning on day 10 of estrous cycle +3. Ovaries were recovered 6 h after GnRH administration to assess development of pre-ovulatory follicles. The proportion of ewes that exhibited estrus after PGF2α and GnRH treatment on cycle 0 was not different (P>0.05) between short- and long-cycle ewes. Onset of estrus occurred sooner (P<0.05) after PGF2α injection in short-cycle ewes than in long-cycle ewes (1.9±0.1 days and 2.3±0.1 days, duration of cycle 0 was 11.9 and 12.3 days, respectively). Duration of estrous cycle +1 was 1.2 days longer (P<0.01) than cycle −1 in short-cycle ewes. However, duration of estrous cycle +1 did not change (P>0.05) after PGF2α and GnRH administration in ewes having long cycles. Pre-ovulatory follicles did not differ (P>0.05) in numbers, diameter, layers of granulosa cells nor concentrations of progesterone and estradiol-17β in follicular fluid between short- and long-cycle ewes after PGF2α and GnRH treatment. In conclusion, ewes having short or long estrous cycles responded differently to PGF2α and GnRH treatment with respect to the interval to onset of estrus and duration of the subsequent estrous cycle.

Resynchrony of previously anoestrous cows and treatment of cows not detected in oestrus that had a palpable corpus luteum with prostaglandin F2𝛂

AIMS: To determine if resynchrony, using a progesterone (P4)/ oestradiol benzoate (ODB) regime, of previously treated, anovulatory anoestrous (AA) cows would increase the probability of oestrus, conception and pregnancy compared to no resynchrony. Additionally, the effect of prostaglandin F2𝛂 (PG) treatment of cows not detected in oestrus, but in which a corpus luteum (CL) was palpable transrectally (NDO/CL+), was compared with no treatment. METHODS: Cows not detected in oestrus by 1 week before the start of the seasonal breeding programme were categorised as AA or NDO/CL+, based on absence or presence of a palpable CL, respectively. All AA cows were treated with an intravaginal device containing 1.36 g P4 (CIDR-B) for a period of 6 days, and with 1 mg ODB by intramuscular (I/M) injection 1 day after the device was removed (Day 0). Half the AA cows that were detected in oestrus between Days 0 and 3 were randomly assigned to be resynchronised by reinsertion of a clean used CIDR-B device on Day 15, for a period of 6 days, followed by an I/M injection of 0.5 mg ODB, 1 day after the device was removed (resynchrony, RS), while the other half were not resynchronised (no-RS). NDO/CL+ cows were alternately assigned to be either treated with 25 mg of the PG, dinoprost tromethamine, on Day 0 or left as untreated controls (Con). RESULTS: Resynchrony increased the percentage of cows detected in oestrus between Days 14 and 28 (212/282 = 75.2% vs 155/285 = 54.4%, for RS vs no-RS, respectively; p<0.001), but had no effect on conception rate to a service within the first 3 days of the mating period (146/397 = 36.8% vs 148/399 = 37.1%, for RS vs no-RS cows, respectively; p>0.9), or to a service between Days 14 and 28 (84/159 = 52.8% vs 114/217 = 52.5%, for RS vs no-RS cows, respectively; p>0.9). Resynchrony increased the Day 28 pregnancy rate (264/432 = 61.1% vs 237/ 435 = 54.5%, for RS vs no-RS cows, respectively; p=0.03), but had no effect on the Day 56 or final pregnancy rates (p>0.1). Prostaglandin treatment of NDO/CL+ cows did not affect the percentage of cows detected in oestrus by Day 7 (43/106 = 40.6% vs 51/101 = 50.5%, for Con vs PG, respectively; p=0.15), or Day 28 (92/106 = 86.8% vs 91/101 = 90.1%, for Con vs PG, respectively; p>0.4). Treatment did not affect the Day 28 pregnancy rate (55/103 = 53.4% vs 54/98 = 55.1%, for Con vs PG, respectively; p>0.9), the Day 56 pregnancy rate (81/ 103 = 78.6% vs 74/98 = 75.5%, for Con vs PG, respectively; p>0.6), or the final pregnancy rate (98/103 = 95.1% vs 89/97 = 91.8%, for Con vs PG, respectively; p>0.3). CONCLUSIONS: Resynchrony of AA cows treated using the present protocol increased the proportion of non-pregnant cows detected in oestrus between Days 14 and 28 and increased the Day 28 pregnancy rate. This resynchrony protocol may be useful for increasing the proportion of the herd pregnant in the first month of the breeding programme, especially in herds that have a history of a low proportion of non-pregnant cows detected in oestrus between Days 14 and 28. There was no benefit in treating NDO/CL+ cows with PG compared to no treatment.

Prostaglandin-induced activation of uterine contractility in pregnant rats does not involve potassium channels

OBJECTIVE: The uterus is a target for prostaglandins, especially at the end of gestation. Whether potassium channels are involved in the effect of prostaglandins is not clear. The aim of this study was to find out. STUDY DESIGN: Concentration-response relationships to prostaglandins (prostaglandin F2α, prostaglandin E2, and prostaglandin I2 [carbacyclin]; 10−10 mol/L-10−4 mol/L) were studied in isolated uterine rings from mid pregnancy (day 14) and late pregnancy (day 21) rats (Krebs solution, 5% CO2in air, 37°C; pH, 7.4). Rings were incubated for 30 minutes with either solvent or adenosine triphosphate-sensitive potassium channel inhibitor or opener glibenclamide and levcromakalim or with calcium-sensitive potassium channel inhibitor or opener NS1619 and iberiotoxin, respectively. The changes in integral activity were compared after each concentration of the agent and were expressed as a percent of the basal integral activity. RESULTS: The increases in spontaneous contractile activity induced by prostaglandin E2 and carbacyclin, but not prostaglandin F2α, were statistically significantly higher in tissues from late pregnancy versus mid pregnancy rats and were not affected by any of the K-channel openers or inhibitors. CONCLUSION: Adenosine triphosphate-sensitive and calcium-sensitive potassium channels are not involved in the effect of prostaglandin F2α, prostaglandin E2, and prostaglandin I2 on pregnant rat uterus. (Am J Obstet Gynecol 2002;186:453-7.)

Effects of prostaglandin F2 alpha on intracellular pH, intracellular calcium, cell shortening and L-type calcium currents in rat myocytes.

We have studied the mechanisms underlying the positive inotropic action of prostaglandin F2 alpha (PGF2 alpha) by monitoring intracellular calcium transients, intracellular pH, L-type calcium currents and cell shortening in isolated ventricular myocytes. Rat myocytes were loaded with fura-2AM for intracellular calcium measurements, or BCECF-AM for pH measurements. Cell shortening was recorded using an edge detection system, and L-type calcium currents measured using whole cell patch clamping. PGF2 alpha (3 nmol l-1-3 mumol l-1 increased single myocyte shortening and reduced resting cell length in a concentration-dependent manner. While myocyte shortening was increased by PGF2 alpha, this was not associated with any change in the amplitude of intracellular calcium transients, diastolic calcium, or L-type calcium currents. However, the same myocytes were capable of responding to catecholamines with increases in calcium transient amplitude and L-type calcium currents. PGF2 alpha (3 mumol l-1 caused a reversible rise in intracellular pH of 0.08 +/- 0.01 pH units (n = 5, p < 0.05). The Na(+)-H+ exchanger inhibitor, HOE 694 (10 mumol l-1, abolished the PGF2 alpha-induced rise in pH and the increase in cell shortening. PGF2 alpha-induced increases in cell shortening and intracellular pH were also attenuated by the protein kinase C (PKC) inhibitor, chelerythrine (2 mumol l-1. The positive inotropic action of PGF2 alpha appears to be mediated via activation of the Na(+)-H+ exchanger with the possible involvement of PKC. This suggests that PGF2 alpha-produces intracellular alkalosis, which then sensitizes cardiac myofilaments to calcium.

Acute effects of prostaglandin F2 alpha, luteinizing hormone, and estradiol on second messenger systems and on the secretion of oxytocin and progesterone from granulosa and early luteal cells of the ewe.

Previous reports have suggested that gonadotropins, estradiol, and prostaglandin F2 alpha (PGF2 alpha) have varying effects on progesterone and oxytocin synthesis or secretion in cultured granulosa and luteal cells collected at different stages of the estrous cycle. The experiments reported here were designed to investigate whether effects of these agonists on secretion of hormones and their coupling to second messenger systems changed around the time of ovulation. Granulosa cells and Day 2 luteal cells of the ewe were cultured for three days and then treated for 30 min with varying doses of PGF2 alpha, LH, or estradiol. LH increased intracellular cAMP at both stages, but granulosa cells were more responsive in terms of both minimum effective dose (10 compared with 100 ng/ml) and degree of stimulation. LH caused no change in intracellular inositol phosphate levels. Both granulosa and early luteal cells responded to LH treatment by an increase in progesterone output in a dose-responsive fashion. PGF2 alpha increased inositol phosphate accumulation in cells collected at both stages of the cycle. All doses tested (10(-6)-10(-8) M) stimulated the release of oxytocin into the culture medium from both granulosa and luteal cells. Progesterone secretion was also increased, but only at the highest dose (10(-6) M). Estradiol treatment (10(-6) M) did not affect either the inositol phosphate or cAMP second messenger systems, but it did inhibit the secretion of oxytocin from granulosa cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Luteolytic effect of prostaglandin F2α in Boran and Boran × Friesian cross-bred heifers

SUMMARYThe luteolytic effect of prostaglandin F2α (PGF2α) during the confirmed luteal phase of the oestrous cycle was evaluated in ten Boran and ten Boran × Friesian cross-bred heifers. Following injection with 25 mg Lutalyse, animals were bled every 6 h for 96 h and plasma progesterone (P4) determined by the ELISA technique. Borans had significantly (P &lt; 0·05) smaller corpora lutea (12·01±0·72 ν. 17·03±2·10 mm) and responded faster to PGF2α injection (65·57±1·40 ν. 78·27±2·18 h) than the cross-bred heifers. However, there was no significant difference in either the initial P4 values (6.24±0·98 ν. 8·00±1·71 ng/ml) or the rate of its decline following PGF2α injection between the two breeds. Values declined sharply to basal levels (11% of the initial pretreatment values) within 48 h in both breeds. All ten cross-breds and eight Borans showed standing oestrus within a week of treatment. However, oestrus was better synchronized (P &lt; 0·05) in Borans than cross-breds. It was concluded that PGF2α is effective for oestrus synchronization in both breeds, but oestrus occurred earlier and was more precise in Borans than in cross-breds.