Effect of prostaglandin F2 alpha (PGF2 alpha) on sources of progesterone and pregnancy in intact, ovariectomized and hysterectomized 90-100 day pregnant ewes.

A single dose of 8 or 16 mg of PGF2 alpha per 58 kg body weight was injected intramuscular into intact, ovariectomized or hysterectomized 90-100 day pregnant sheep in three separate experiments. Both doses of PGF2 alpha decreased the weights of the corpora lutea (P less than or equal to 0.05) and the concentration of progesterone in ovarian venous plasma at 72 hr (P less than or equal to 0.05) compared to the 0 hr sample within treatment groups and to control ewes at 72 hr in intact and hysterectomized pregnant ewes. In hysterectomized pregnant ewes, progesterone in jugular plasma declined (P less than or equal to 0.05) from 0 to 72 hr but never fell below 4 mg/ml and this decrease in progesterone after 8 or 16 mg PGF2 alpha was greater than in control hysterectomized ewes (P less than or equal to 0.05). There was a significant decrease in progesterone over time in jugular or uterine venous plasma in the presence of absence of the ovaries in 90-100 day pregnant ewes (P less than or equal to 0.05) but the profiles of progesterone were not different between vehicle and PGF2 alpha-treated ewes (P greater than or equal to 0.05). Uterine venous progesterone never declined below 30 ng/ml in the presence or absence of the ovaries and there was a significant quadratic increase (P less than or equal to 0.05) in uterine venous progesterone toward the end of the 72 hr sampling period indicating an increase in steroidogenic activity of the placenta. PGF2 alpha did not affect the number of abortions in intact or ovariectomized pregnant ewes (P greater than 0.05). Thus, the corpus luteum of sheep at 90-100 days of pregnancy is functional and responsive to PGF2 alpha, placentomes are functional but do not appear to be responsive to the doses of PGF2 alpha tested and PGF2 alpha was not an abortifacient over the 72 hr treatment period.     

Effect of indomethacin, cycloheximide, and aminoglutethimide on ovarian steroid and prostanoid levels during ovulation in the gonadotropin-primed immature rat

It has become popular to use the gonadotropin-primed immature rat to study ovulation. The ovarian content of progesterone, estradiol, PGE2, PGF2 alpha, and 6-keto-PGF1 alpha during the ovulatory process was determined in this model. Also, the effect of three anti-ovulatory agents on the ovarian levels of the above substances was determined. At 23 days of age, Wistar rats were primed with pregnant mares serum gonadotropin (PMSG) sc, and two days later the ovulatory process was initiated with human chorionic gonadotropin (hCG) sc. The ovarian follicles began rupturing 12 h later. Ovaries were assayed for the two steroids and prostanoids at 2-h intervals before and several 4-h intervals after ovulation. The ovarian estradiol level increased slightly between 0 and 2 h after hCG, while the progesterone level increased sharply between 2 and 4 h after hCG--at a time when the estradiol declined markedly. All three prostanoids increased concomitantly with progesterone. When the PG synthesis was blocked by indomethacin treatment at 1 h before hCG, ovarian progesterone levels still increased. In contrast, when steroidogenic activity was inhibited by aminoglutethimide, the ovarian prostanoid levels also decreased. Cycloheximide had little effect on the steroids and prostanoids. It is concluded that ovarian prostanoid synthesis might be influenced by ovarian steroid output.     

Effects of indomethacin and prostaglandins on ovulation of goldfish.

A technique is described whereby elevated temperature and HCG injection yield a high percentage of ovulation in gravid goldfish. Indomethacin (10 mug/g; i.p. injection) completely inhibits ovulation if given within 6 hours following HCG (4 IU/g); the unovulated oocytes develop rapidly into corpora atretica. PGE1, PGE2, and PGF2alpha (5 mug/g; i.p. injection) induce ovulation in fish treated with indomethacin and HCG; PGE2 was most effective when given 11 hours after HCG. The results suggest that the ovulatory action of prostaglandins following HCG stimulation is at the level of the ovary and that it is restricted to a period between 7 and 12 hours after the gonadotropin injection.     

Effectiveness of prostaglandin f 2 alpha in restoration of HMG-HCG induced ovulation in indomethacin-treated rhesus monkeys.

Six mature female rhesus monkeys were treated with HMG-HCG in control cycles at doses adjusted to induce ovulation while avoiding superovulation. Occurrence of ovulation was determined by observation of fresh ovulation points at laparotomy 48 to 120 hours following HCG. In subsequent cycles animals were treated with indomethacin (treatment days 4 through 10) together with the established dose of HMG-HCG. In 8 cycles indomethacin 5 mg/kg was given i.m. once daily; in 9 cycles 10 mg/kg i.m. was administered in 2 divided doses. Following this, PGF2alpha (3 mg t.i.d. s.c.) was administered for 3 days together with indomethacin 10 mg/kg and HMG-HCG, beginning on the day prior to HCG. Determinations of progesterone were performed by RIA on treatment days 4, 7, 10, and 11. Eleven of the 13 control cycles were ovulatory. With indomethacin 5 mg/kg/day, 5 of 8 cycles were ovulatory but ovulation was delayed in 2 instances. Of 9 cycles using indomethacin 10 mg/kg/day only 1 was ovulatory. When PGF2alpha was administered in susequent cycles along with indomethacin (10 mg/kg) and HMG-HCG, ovulation occurred in 13 of 19 cycles. These data suggest that local ovarian PGF2alpha may be essential in the mechanics of follicle rupture in gonadotropin-treated rhesus monkeys.     

The effects of ovarian steroids in controlling rat uterine prostaglandin F2-alpha during the peri-implantation period

Rats with delayed implantation, induced by ovariectomy or hypophysectomy, as well as those with normal pregnancy were used to examine the changes in uterine prostaglandin F2 alpha (PGF2 alpha) associated with implantation. In normal pregnant rats, while maximal uterine production of PGF2 alpha was found at 09:00, maximal catabolic enzyme activity (CEA) was seen at 17:00 of day 4. Uterine content of PGF2 alpha was high at 17:00 of day 4, but decreased by 80% within the next 24 h. There was no change in PGF2 alpha production during the first 6 h after injection of estradiol to hypophysectomized animals. There was, however, a dramatic decrease in production within the next 6 h. In contrast, CEA was not different in animals treated with estrogen than in those receiving only progesterone. In ovariectomized animals, uterine PGF2 alpha production also was lowered by estrogen but in these animals CEA was significantly elevated 18 h after injection of estradiol. Estrogen caused a greater increase in PGF2 alpha content in the hypophysectomized, compared to the ovariectomized, rats. The results are consistent with the view that ovarian steroids play an important role in controlling the changes in uterine PGF2 alpha around the time of implantation in rat.     

Regulation of estrus and ovulation in mares with progesterone or progesterone and estradiol biodegradable microspheres with or without PGF2alpha

A single injection of a microsphere preparation, designed to deliver 1.25 gm progesterone and 100 mg estradiol-17beta at a controlled rate, for a duration of 12 to 14 days, produces accurate control of estrus and fertile ovulations in mares. Theatment is followed by PGF(2)alpha injection 14 days after steroid injection. The objectives of the present study were to determine whether estradiol added to the progesterone treatment or PGF(2)alpha administered at the end of the steroid treatment regimen, would improve synchronization of estrus and ovulation. A total of 45 cyclic horse mares was randomly assigned to 1 of 5 treatment groups as follows: Group 1 (control, n=9) sterile microsphere vehicle + sterile PGF(2)alpha vehicle 14 days after treatment with microsphere vehicle; Group 2 (n=9) progesterone and estradiol microspheres + PGF(2)alpha 14 days after treatment with microspheres; Group 3 (n=9) progesterone and estradiol microspheres + PGF(2)alpha vehicle 14 days after treatment with microspheres; Group 4 (n=9) progesterone + PGF(2)alpha 14 days after treatment with microspheres; and Group 5 (n=9) progesterone + PGF(2)alpha vehicle 14 days after treatment with microspheres. Addition of estradiol (P<0.05) or PGF(2)alpha (P<0.05) to the treatment regimen increased synchronization efficary by reducing variation in days to ovulation. All treatments significantly reduced variation in days to estrus compared with that of the controls; however, mares in the progesterone groups had an increased incidence of silent or shortened estrous behavior (<- 2 days) following treatment. Estradiol added to the treatment regimen increased (P<0.05) the number of mares with post treatment estrus > 2 days in duration compared with mares treated with progesterone (78 vs 33%, respectively). Therefore, estradiol and PGF(2)alpha each appear to reduce variation in days to ovulation while estradiol seems to promote better expression of posttreatment estrous behavior.     

Progesterone, 20α-dihydroprogesterone and PGF; Interrelated hormonal changes during pseudo-pregnancy in the rat

Ovarian and uterine tissue concentrations of progesterone, 20α-dihydroprogesterone (20_αOHP) and prostaglandin F (PGF) were measured during hormonally-induced pseudopregnancy, as were plasma levels of progesterone and 20αOHP, in hysterectomised and sham-operated rats. Elevated levels of PGF in uterine and ovarian tissues were coincident with declining concentrations of progesterone and increasing concentrations of 20αOHP in the sham-operated rats. Maximum PGF concentrations were apparent in uterine tissue 14 days after hCG injection, coincident with the plasma, ovarian and uterine nadir concentrations of progesterone. A small but statistically significant increase in ovarian PGF was apparent at this time in sham-operated rats. This elevation of ovarian PGF was abolished by hysterectomy.     

The effect of indomethacin on ovarian prostaglandin release in hens

Indomethacin, an inhibitor of prostaglandin (PG) synthetase, will block uterine muscle electromyographic activity (EMG activity) and oviposition at a midsequence oviposition and ovulation in domestic hens, but does not block the increase in EMG activity associated with the first ovulation of a sequence. To assess the potential relationship between prostaglandin release from the ovarian follicles and EMG activity in egg-laying hens, we determined the concentrations of PGF2 alpha, 13,14-dihydro-15-keto-PGF2 alpha (PGFM), and PGE2 in brachial, ovarian follicular and uterine venous plasma and tissues in relation to uterine muscle EMG activity at the first ovulation and at a midsequence oviposition. The concentrations were measured after an i.m. injection (25 mg/hen) of indomethacin. In control hens sampled hourly, beginning 4 h before the peak of EMG activity at the first ovulation of a sequence, there was a sharp increase (p less than 0.05) in concentrations of PGF2 alpha and PGFM in brachial vein plasma coincident with the increase (p less than 0.05) in uterine EMG activity. Hens pretreated with indomethacin also had increased plasma PGF2 alpha and PGFM levels (p less than 0.05) in brachial vein plasma and increased uterine EMG activity (p less than 0.05) at this time. Indomethacin treatment lowered but did not eliminate mean levels of PGF2 alpha in the venous effluent from the largest preovulatory follicle at the first ovulation (36.0 +/- 9.9 ng/ml vs. 14.4 +/- 1.8 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of hysterectomy and uterine decidualization on in vivo levels of prostaglandins in the corpus luteum of adult pseudopregnant rats

A possible role of the uterus in regulating content of luteal prostaglandins (PGs) was investigated. Pseudopregnancy was induced in adult virgin female rats by mating them with vasectomized male rats. On Day 5 of pseudopregnancy, decidualization of the uterus was induced or hysterectomy was performed. As controls, intact pseudopregnant animals with a luteal phase of 13 +/- 1 days were used. Measurements of in vivo tissue levels of PGF2 alpha, PGE2, and 6-keto-PGF1 alpha were performed by RIA after homogenization and extraction procedures in CL of pseudopregnancy and remainder of ovaries on Days 5, 13, and 19. Serum levels of progesterone and 20 alpha-dihydroprogesterone were determined by RIA. In hysterectomized animals, PGF2 alpha levels increased 2.5-fold in corpora lutea on Day 13 compared with levels on Day 5 of pseudopregnancy, but were still lower than in control rats undergoing functional luteolysis on Day 13. Decidual-tissue-bearing rats exhibited low levels of PGF2 alpha on Day 13 of pseudopregnancy. On Day 19, when luteolysis had occurred in decidual-tissue-bearing and hysterectomized rats, as judged by plasma levels of progestins, luteal content of PGF2 alpha was elevated to a similar level as that in control animals undergoing functional luteolysis on Day 13. When data pooled from control, decidual-tissue-bearing and hysterectomized rats were analyzed, a highly significant inverse correlation (r = -0.72, n = 46, p less than 0.001) between luteal PGF2 alpha content and ratio of plasma progestins was found.(ABSTRACT TRUNCATED AT 250 WORDS)     

Response of the 1-5 day-aged ovine corpus luteum to prostaglandin F2alpha

The hypothesis that, in the ewe, prostaglandin (PG) F2alpha administration on day 3 after ovulation is followed by luteolysis and ovulation was tested using 24 animals. The ewes were treated with a dose of a PGF2alpha analogue (delprostenate, 160 microg) on days 1 (n=8), 3 (n=8) or 5 (n=8) after ovulation, was established by transrectal ultrasonography. Daily scanning and blood sampling were performed to determine ovarian changes and progesterone serum concentrations by radioinmunoassay. The treatment induced a sharp decrease of progesterone concentrations followed by oestrus and ovulation in all ewes treated on days 3 and 5 and in one ewe treated on day 1 (8/8, 8/8, 1/8; P<0.05). Seven ewes treated on day 1 did not respond to PGF2alpha treatment and had an inter-ovulatory cycle of normal length (17.4 +/- 0.5 days). However, the profile of progesterone concentrations during the cycle of these ewes was delayed 1 day (P<0.05) compared with a control cycle. The overall interval between PGF2alpha and oestrus for the 17 responding ewes was 42.4 +/- 2.3 h. In 15 of these ewes the ovulatory follicle was originated from the first follicular wave and the ovulation occurred at 60.8 +/- 1.8 h after PGF2alpha treatment. The other two responding ewes ovulated an ovulatory follicle originated from the second follicular wave between 72 and 96 h after treatment. These results support the hypothesis and suggest that refractoriness to PGF2alpha of the recently formed corpus luteum (CL) may be restricted to the first 1-2 days post-ovulation.     

LH surge in Nelore cows (Bos indicus), after induced estrus or after ovarian superestimulation

Considering that there is limited information about the preovulatory LH surge in Zebu cattle (Bos indicus), the purpose of the present work was to assess the LH surge in Nelore cows during the estrous cycle and after ovarian superestimulation of ovarian follicular development with FSH. This information is particularly important to improve superovulatory protocols associated with fixed-time artificial insemination. Nelore cows (n=12) had their estrus synchronized with an intravaginal device containing progesterone (CIDR-B) associated with estradiol benzoate administration (EB, 2.5 mg, i.m., Day 0). Eight days later all animals were treated with PGF2alpha (Day 8) in the morning (8:00 h) and at night, when CIDR devices were removed (20:00 h). Starting 38h after the first PGF2alpha injection, blood sampling and ovarian ultrasonography took place every 4h, during 37 consecutive hours. Frequent handling may have resulted in a stress-induced suppression of LH secretion resulting in only 3 of 12 cows having ovulations at 46.7+/-4.9 and 72.3+/-3.8 h, respectively, after removal of CIDR-B. Thirty days later, the same animals received the described hormonal treatment associated with FSH (Folltropin), total dose=200 mg) administered twice a day, during 4 consecutive days, starting on Day 5. Thirty-six hours after the first injection of PGF2alpha, to minimize stress, only seven blood samples were collected at 4h interval each, and ultrasonography was performed every 12 h until ovulation. In 11 of 12 cows (92%) the LH surge and ovulation were observed 34.6+/-1.6 and 59.5+/-1.9 h, respectively, after removal of progesterone source. The maximum values for LH in those animals were 19.0+/-2.6 ng/ml (mean+/-S.E.M.). It is concluded that, in Nelore cows submitted to a ovarian superstimulation protocol, the LH surge occurs approximately 35 h after removal of intravaginal device containing progesterone, and approximately 12h before the LH surge observed after an induced estrus without ovarian superstimulation.     

Efficacy of PGF(2alpha) to synchronize estrus in water buffalo cows (Bubalus bubalis) is dependent upon plasma progesterone concentration,corpus luteum size and ovarian follicular status before treatment

This study was conducted to identify factors affecting PGF(2alpha) efficacy to synchronize estrus in water buffalo cows. After detection of a corpus luteum (CL) by rectal palpation, cows were treated (im) with dinoprost (12.5, 25 or 50mg) or D(+) cloprostenol (75, 150 or 300 microg) in a total of 66 treatments. Blood samples were collected 0, 24 and 48 h after treatment and ultrasound examinations and observations for estrus were performed daily to the day of ovulation or to 6 days after treatment. No PGF(2alpha) dose-response pattern was observed and overall rates of luteal regression (progesterone <1.0 ng/ml at 48 h), estrus, no detected behavioral estrus with ovulation occurring, and ovulation were 71.2, 36.4, 19.7 and 54.5%, respectively. To analyze plasma progesterone concentrations and ovarian dynamics, cows were divided in three groups according to their response to treatment. Cows that failed to have ovulations from a follicle after treatment (Group A, n = 30) had (P < 0.05) a lower plasma progesterone concentration (2.98 ng/ml) and smaller CL area (CLA; 187.3 mm(2)) before treatment as compared with cows that had an ovulation from a follicle (4.43 ng/ml and 223.7 mm(2), respectively; Groups B and C, n = 36). In cows that failed to ovulate, plasma progesterone concentration decreased in the first 24 h, but did not decline further and was >1.0 ng/ml 48 h after treatment. Moreover, no significant change in CLA after treatment was detected, indicating that treatment induced only partial luteolysis. In cows that ovulated, plasma progesterone concentration and CLA decreased continuously from treatment to ovulation (consistent with complete luteolysis). Threshold values of 2.8 ng/ml for plasma progesterone concentration and 189 mm(2) for CLA were identified as the best predictors of ovulation before treatment (83.3 and 80.6% sensitivity and 58.6 and 65.5% specificity, respectively, with positive and negative predictive values around 71%). When the origin of the ovulatory follicle was investigated, the interval from treatment to ovulation was shorter (91.9 versus 113.3 h; P < 0.05), and the ovulatory follicle had a slower growth rate (1.02 versus 1.55 mm per day; P < 0.005), a lesser increase in diameter from treatment to ovulation (4.7 versus 8.0 mm; P < 0.001), and a greater maximum diameter (13.2 versus 12.1 mm; P < 0.05) in cows that ovulated from the largest follicle present in the ovary before treatment (Group B, n = 27) compared with cows that ovulated from the second largest follicle present in the ovary before treatment (Group C, n = 9). In summary, the efficacy of PGF(2alpha) for causing luteolysis and synchronizing estrus and ovulation in buffalo cows was dependent upon plasma progesterone concentration, CL size and ovarian follicular status before treatment.     

Regulation of hysterectomy induced derangements in ovarian carbohydrate metabolism in albino rats. II. Role of prostaglandin F2 alpha.

Wistar strain albino rats were subjected to bilateral hysterectomy surgically and the ovarian carbohydrate metabolism of these animals was compared with sham operated controls. The ovarian glycogen content of hysterectomized animals was elevated with inhibition of glycogenolysis, hexose mono and diphosphate pathways and oxidative metabolism. Administration of PGF2 alpha to hysterectomized animals led to activation of ovarian glycogenolysis and other pathways of carbohydrate metabolism of hysterectomized animals was restored towards normal level after PGF2 alpha substitution.     

Reduction by human chorionic gonadotropin of the luteolytic effect of prostaglandin F2 alpha in ewes

The ability of human chorionic gonadotropin (HCG) to reduce the luteolytic effect of prostaglandin (PGF2 alpha) was demonstrated in cycling ewes. As expected, treatment with 10 mg of PGF2 alpha alone on Day 10 of the estrous cycle exerted a potent negative effect on the function and structure of corpus luteum (CL) as indicated by reduced plasma progesterone, CL progesterone, and CL weight. However, the identical PGF2 alpha treatment failed to significantly reduce either luteal function or luteal weight when administered to ewes that were also treated with HCG on Days 9 and 10 of the estrous cycle. Treatment with HCG alone had a positive effect on CL as indicated by increased plasma progesterone, CL progesterone, and CL weight. Treatment with HCG did not render the CL totally insensitive to the negative effects of PGF2 alpha because plasma progesterone was reduced when the dose of PGF2 alpha was doubled. Whether CL regressed or continued to function after treatment with both HCG and PGF2 alpha appeared to depend upon a balance between the positive and negative effects of the two hormones.     

Relative roles of oestradiol and of the uterus in the maintenance of the corpus luteum in the pseudopregnant brown hare (Lepus europaeus)

Brown hares were made pseudopregnant by sterile matings or PMSG-hCG treatment (day of mating or hCG injection = Day 0 of pseudopregnancy). Progesterone secretion by the CL began 3-4 days after the ovulatory stimuli, reached maximum on Days 8 to 11 and decreased thereafter to reach low levels from Day 9 to 18, depending on the female. Cauterization of all large ovarian follicles on Day 7 resulted in an immediate luteolysis in young females, but had no effect in older ones. Oestradiol capsules implanted from Day 7 to Day 46 were able to maintain progesterone secretion until at least Day 30, in intact females as well as in females with all large follicles cauterized. Hysterectomy on Day 7 or 8 was followed by an immediate drop in progesterone concentrations; oestradiol capsules implanted at the time of hysterectomy prevented the drop in progesterone values, which remained elevated until Day 38. The induction of ovulation in females hysterectomized 2 months before resulted in CL of slightly shortened life-span. The injection of PGF-2 alpha on Day 7 of pseudopregnancy was followed by an immediate luteolysis. These results suggest that oestradiol secreted by the large ovarian follicles is the main luteotrophic factor in the brown hare. In old hares, the large amount of interstitial tissue could secrete oestrogens, and thus maintain pseudopregnancy. On Day 7 of pseudopregnancy, the uterus secretes a luteotrophic substance acting either directly on the ovary, or via the pituitary, to maintain oestradiol secretion by the follicles. In long-term hysterectomized females, the CL would be able to develop independently of any trophic substance, but for a reduced duration.     

Progesterone and estradiol secretion by porcine luteal cells is influenced by individual and combined treatment with prostaglandins E2 and F2alpha throughout the estrus cycle.

The present experiments were conducted to test whether the ratio of PGE2:PGF2alpha affects steroid secretion by porcine luteal cells. We examined the effect of separate and combined treatment with PGE2 and PGF2alpha on progesterone and estradiol secretion. Luteal cells were collected at three different stages of the luteal phase (1-3 days after ovulation; 10-12 days after ovulation and 14-16 days after ovulation). PGE2 alone in a dose dependent manner increased progesterone production by cells collected from mature corpora lutea. On the other hand, PGF2alpha in a dose dependent manner decreased progesterone secretion by cells of the same origin. Progesterone secretion by cells isolated from mature and regressing corpora lutea and treated with both prostaglandins increased in comparison to PGF2alpha-treated cultures. However, in cells collected from regressing corpora lutea PGE2 and PGF2alpha in a ratio of 2:1 and 4:1 increased estradiol production when compared to control and both ratios increased estradiol secretion in comparison to PGF2alpha-treated cells. These data 1) confirm the luteotropic effect of PGE2 and the luteolytic effect of PGF2alpha; 2) demonstrate that when the ratio of PGE2 to PGF2alpha changed from 1:1 to 2:1 or 4:1 cells were protected against the inhibitory effects of PGF2alpha on progesterone secretion by cells collected during the mid- and late luteal phase; and 3) suggest that elevated estradiol production by luteal cells, isolated during late luteal phase, under the influence of increased doses of PGE2 may serve as an additional source of estradiol to blastocysts, during early pregnancy in the pig.     

The effect of a GnRH analogue on the dynamics of follicular development and synchronization of estrus in lactating cyclic dairy cows

A GnRH analogue was used to synchronize ovarian follicular development prior to an injection of PGF(2alpha) for the synchronization of estrus in lactating Holstein cows. On Day 12 (estrus = Day 0) of the experimental cycle, cows (n = 8) were injected with 8 mug Buserelin (BUS group), followed by 25 mg PGF(2alpha) 7 d later (Day 19). Control cows (n = 7) received PGF(2alpha) on Day 12 (PGF group). Ovaries were scanned daily via ultrasonography, and plasma progesterone and estradiol concentrations were determined. Sizes of all visible follicles were recorded. Follicles were classified as small (3 to 5 mm), medium (6 to 9 mm), or large (>/= 10 mm). Between Days 12 and 16 of the cycle, the number of large follicles in PGF cows remained unchanged (1.2), whereas in the BUS group, the number of large follicles decreased from 1.3 on Day 12 to 0.5 on Day 15. Only 4 of 7 PGF cows ovulated a second-wave dominant follicle. In the BUS group, 7 of 8 cows ovulated a GnRH analogue induced dominant follicle that was first identified on Day 15. During the follicular phase (last 5 d prior to estrus), plasma progesterone declined in association with CL regression in both groups, and estradiol concentrations increased, reaching higher (P<.0.05) preovulatory peak concentration in BUS cows than in PGF cows (14.0 +/- 1.0 vs 10.4 +/- 1.1 pg/ml). The number of medium-size follicles was smaller and the number of small-size follicles tended to be higher in BUS cows than in the PGF-treated group. On the day of estrus, the size of the ovulatory follicle (16.1 vs 13.3 mm) and the size difference between the ovulatory and second largest follicle (11.4 vs 6.2 mm) were both larger in BUS cows than in PGF-treated cows, suggesting a more potent dominance effect of the ovulatory follicle in the BUS cows. This study suggests that a GnRH analogue can alter follicular development prior to synchronization of estrus with an injection of PGF(2alpha) in lactating dairy cows.     

Strategies to optimize reproductive efficiency by regulation of ovarian function in yak (Poephagus grunniens L.)

Ovulatory response to the first GnRH of Ovsynch is the critical determinant for successful synchronization of ovulation in animals. An attempt was made in this study to design a pre-Ovsynch hormonal strategy in yaks to increase the ovulatory response to the first GnRH injection of Ovsynch so that overall synchronization rate to Ovsynch could be improved. Non-lactating cyclic yak cows (n=33) were assigned to receive either no treatment before Ovsynch (control) or 0.375 mg of PGF2alpha (PreP) followed 2 d later by 10 microg of GnRH (PreG), administered 4 (G4G), 5 (G5G), or 6 (G6G) d before initiating the Ovsynch protocol. Rectal palpation was performed to assess ovulation and blood samples were collected to measure progesterone concentrations during pre-treatment, treatment and post-treatment periods. All the animals received timed AI 12 and 24h after the final GnRH of Ovsynch. Diagnoses for pregnancy were performed by rectal palpation and profiles of plasma progesterone 35 d after AI. Percentage of yak cows that ovulated in response to the first GnRH injection of Ovsynch, synchronized to Ovsynch treatment, had a functional CL at PGF2alpha of Ovsynch, had circulating concentrations of P4 at PGF2alpha of Ovsynch and likely to be pregnant after 35 d after AI, were greater in G6G and G5G compared with control, whereas G4G did not differ from controls. In addition, animals that ovulated in response to first GnRH of Ovsynch had greater response to PGF2alpha of Ovsynch and greater synchronization rate to the overall protocol than those that did not ovulate. In summary, PGF2alpha-and-GnRH-based pre-Ovsynch strategies consisting of 5 or 6-d interval between PreG and first GnRH of Ovsynch resulted in a greater ovulatory and luteolytic response to first GnRH andPGF2alpha of Ovsynch, respectively, compared with control animals. These, in turn, optimized synchronization rate to Ovsynch in yaks.     

Comparison of endocrine changes,timing of ovulations,ovarian follicular growth,and efficacy associated with Estradoublesynch and Heatsynch protocols in Murrah buffalo cows (Bubalus bubalis)

Poor estrus expression and the difficulty encountered in predicting the time of ovulation compromise the reproductive efficiency of Murrah buffalo cows. Synchronization of ovulation and timed artificial insemination are able to precisely control the time of ovulation and thus avoid the need for estrus detection. Recently, the Estradoublesynch protocol (administration of a PGF2α injection 2 days before Heatsynch protocol; GnRH 0, PGF2α 7, estradiol benzoate [EB] 8) was developed that precisely synchronized ovulation twice, i.e., after GnRH and EB injections and resulted in satisfactory pregnancy rates in Murrah buffaloes. The present study was conducted on 104 cycling and 31 anestrus buffaloes to compare (1) the endocrine changes, timing of ovulations, ovarian follicular growth, and efficacy of Estradoublesynch and Heatsynch protocols in cycling and (2) the efficacy of Estradoublesynch and Heatsynch protocols for the improvement of fertility in cycling and anestrus Murrah buffalo cows. Ovulation was confirmed after all GnRH and EB treatments by ultrasonographic examination at 2-hour intervals. Plasma progesterone and total estrogen concentrations were determined in blood samples collected at daily intervals, beginning 2 days before the onset of protocols until the day of second ovulation detection. Ovulatory follicle size was measured by ultrasonography at six time points (first PGF2α administration of Estradoublesynch protocol every 2 days before the onset of Heatsynch protocol, GnRH administration of both protocols, 2 hours before ovulation detection after GnRH administration of both protocols, second PGF2α injection of Estradoublesynch protocol, PGF2α injection of Heatsynch protocol, EB injection of both protocols and, 2 hours before ovulation detection after EB administration of both protocols). Plasma LH, total estrogen, and progesterone concentrations were determined in blood samples collected at 30-minute intervals for 8 hours, beginning GnRH and EB injections, and thereafter at 2-hour intervals until 2 hours after the detection of ovulation. The first ovulatory rate was significantly higher (P < 0.05) in the Estradoublesynch protocol (84.6%) than that in the Heatsynch protocol (36.4%). The first LH peak concentration (74.6 ± 10.4 ng/mL) in the Estradoublesynch protocol was significantly higher (P < 0.05) than that of the Heatsynch protocol (55.3 ± 7.4 ng/mL). In Estradoublesynch protocol, the total estrogen concentration gradually increased from the day of GnRH administration coinciding with LH peak, and then gradually declined to the basal level until the time of ovulation detection. However, in Heatsynch protocol, the gradual increase in total estrogen concentration after GnRH administration was observed only in those buffalo cows, which responded to treatment with ovulation. In both Estradoublesynch and Heatsynch protocols, ovulatory follicle size increased by treatment with GnRH and EB until the detection of ovulation. The pregnancy rate after the Estradoublesynch protocol (60.0%) was significantly higher (P < 0.05) than that achieved after the Heatsynch protocol (32.5%). Satisfactory success rate using the Estradoublesynch protocol was attributed to the higher release of LH after treatment with GnRH, leading to ovulation in most of the animals and hence creating the optimum follicular size at EB injection for ovulation and pregnancy to occur.     

Activity of ovarian nitric oxide synthase (NOs) during ovulatory process in the rat: relationship with prostaglandins (PGs) production.

Nitric oxide (NO) is synthesized by the rat ovary and a role in the follicular development, the ovulation, and the luteal formation has been postulated. The aims this study were to determine the activity of nitric oxide synthase (NOs) enzyme during the ovulatory process and to demonstrate the existence of a relationship between the ovarian NO production and the synthesis of prostaglandins (PGs) involved in the follicular rupture. Prepuberal rats treated with PMSG/hCG to induce ovulation were used. The NOs activity, measured by [(14)C]citrulline formation, showed an increase after PMSG administration and reached a maximum at 10 h after hCG injection. NOs activity remained high up to 24 h post ovulation. At 10 h after the hCG injection, the activity of Ca(2+)-dependent NOs (constitutive NOs) was similar to that seen at 0 h, and the activity of Ca(2+)-independent NOs (inducible NOs) increased from 14.4 to 51% of total activity. The in vitro ovarian production of PGE and PGF(2alpha) was inhibited by L-NAME and stimulated by 3-morpho-linosydnonimine (SIN-1), a NO donor. The in vivo production of ovarian prostaglandins was also inhibited by the intrabursal administration of two NOs inhibitors, N(G)-nitro-L-arginine methyl ester (L-NAME) and N(G)-monomethyl-L-arginine (L-NMMA). Our results suggest that the inducible NOs (iNOs) is the main isoform involved in the ovulatory process and that the NO produced stimulates the synthesis of both PGE and PGF(2alpha) from the cyclooxygenase pathway, to enhance the process of follicle rupture.