Effectiveness of prostagland in F2α 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, PGF₂α (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 PGF₂α was administered in subsequent cycles along with indomethacin (10 mg/kg) and HMG-HCG, ovulation occurred in 13 of 19 cycles. These data suggest that local ovarian PGF₂α may be essential in the mechanics of follicle rupture in gonadotropin-treated rhesus monkeys.     

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 effect of indomethacin of HMG-HCG induced ovulation in the phesus monkey.

The investigation was designed to study the influence of indomethacin on gonadotropin induced ovulation in the rhesus monkey. Six mature female monkeys were treated with HMG-HCG for at least 2 control ovulatory cycles at dosage levels adjusted to induced ovulation while avoiding superovulation. Ovulation was confirmed by observation of the ovaries for fresh ovulation points at laparotomy. Following establishment of an appropriate dosage schedule, treatment was begun with indomethacin (5 mg/kg/day) starting 5 days prior to HCG and continuing to the time of laparotomy. In a second treatment cycle, indomethacin was administered at a dose of 5 mg/kg b.i.d. together with the established dose of HMG-HCG. Ovarian inspection was carried out as in the control cycles. Venous blood was obtained on treatment days 4, 7, 10 and 11 for determination of serum estrone, estradiol and progesterone. Indomethacin administration resulted in ovulation inhibition at a dose of 10 mg/kg/day when ovulation inducing doses of gonadotropins were administered. Peripheral blood steroid levels suggest that follicle maturation and estrogen production was unimparied by indomethacin. These findings indicate that the ovarian synthesis of prostaglandin may be essential in the process of ovulation.     

The effect of indomethacin on HMG-HCG induced ovulation in the rhesus monkey

The investigation was designed to study the influence of indomethacin on gonadotropin induced ovulation in the rhesus monkey. Six mature female monkeys were treated with HMG-HCG for at least 2 control ovulatory cycles at dosage levels adjusted to induce ovulation while avoiding superovulation. Ovulation was confirmed by observation of the ovaries for fresh ovulation points at laparotomy. Following establishment of an appropriate dosage schedule, treatment was begun with indomethacin (5 mg/kg/day) starting 5 days prior to HCG and continuing to the time of laparotomy. In a second treatment cycle, indomethacin was administered at a dose of 5 mg/kg b.i.d. together with the established dose of HMG-HCG. Ovarian inspection was carried out as in the control cycles. Venous blood was obtained on treatment days 4, 7, 10 and 11 for determination of serum estrone, estradiol and progesterone. Indomethacin administration resulted in ovulation inhibition at a dose of 10 mg/kg/day when ovulation inducing doses of gonadotropins were administered. Peripheral blood steroid levels suggest that follicle maturation and estrogen production are unimpaired by indomethacin. These findings indicate that the ovarian synthesis of prostaglandin may be essential in the process of ovulation.     

Luteolytic action of 15-keto prostaglandin F2α in the rhesus monkey

The naturally-occurring metabolite of prostaglandin F_2α, 15-keto prostaglandin F_2α (15-keto PGF_2α), elicited rapid and sustained declines in serum progesterone concentrations when administered to rhesus monkeys beginning on day 22 of normal menstrual cycles. Evidence for luteolysis of a more convincing nature was obtained in studies where a single dose of 15-keto PGF_2α was given on day 20 of ovulatory menstrual cycles in which intramuscular injections of hCG were also given on days 18–20; serum progesterone concentrations fell precipitously in monkeys within 24 hours following intramuscular administration of 15-keto PGF_2α. However, corpus luteum function was impaired in only 4 of 11 early pregnant monkeys when 15-keto PGF_2α was administered on days 30 and 31 from the last menses, a time when the ovary is essential for the maintenance of pregnancy. Gestation failed in 2 additional monkeys 32 and 60 days after treatment with 15-keto PGF_2α, but progressed in an apparently normal manner in the remaining 5 animals. Two pregnant monkeys treated with 15-keto PGF_2α on day 42 from the last menstrual period, a time when the ovary is no longer required for gestation, continued their pregnancies uneventfully. Corpus luteum function was not impaired in 9 control monkeys which received injections of vehicle or hCG at appropriate times during the menstrual cycle or pregnancy.     

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 μg/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 PGF_2α (5 μg/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.     

Effects of indomethacin and prostaglandin F2α on ovulation and ovarian contractility in the rabbit

The present investigation was carried out to determine whether inhibition of ovulation in the rabbit by administration of indomethacin can be correlated with any change in ovarian contractility at ovulation time and can be reversed by administration of prostaglandins. Indomethacin was adminstered intra-muscularly using three different schedules in a dose of 5 mg/kg. A reduced number of ruptured follicles following HCG was noted in all groups treated with indomethacin. Infusion of PGF_2α into the aorta (1 μg/kg/min.) could reverse this effect. Less pronounced ovarian contractility was observed after indomethacin treatment, but infusion of PGF_2α immediately enhanced contractility in ovaries from indomethacin treated rabbits. The inhibition of ovulation in the rabbit associated with indomethacin adminstration may be related to suppression of ovarian contractions. These data also suggest that prostaglandins may play a significant role in the mechanism of ovulation through an influence on ovarian contractility.     

Effect of prostaglandin F2α on ovulation and fertilization in rabbit

The effect of prostaglandin F_2α on ovulation and fertilization was studied in rabbits. The number of ovulation was not affected by subcutaneous injection of PGF_2α but the recovery of ova was significantly decreased when PGF_2α was given either at 12 or 16 h after HCG injection and autopsied 24 h latter. The results suggest that exogenous PGF_2α accelerates ovum transport and expels the eggs prematurely from the female tract and does not impair ovulation or the fertilization processes when given to rabbit at 1 mg/kg B.W.     

Reproductive hormone secretions in pony mares subsequent to ovulation control during late winter

Beginning in December, pony mares were placed under a schedule of increasing light. Starting in February, onset of estrus was checked by daily teasing with a stallion. Mares were randomly assigned to one of three treatments (6 mares per group) administered in March. Treatments were: Group I — 75 mg progesterone injected intramuscularly every day for 10 days in combination with a 1.25 mg injection of PGF₂α on day 7 of progesterone treatment and a 2,000 IU injection of HCG on day 2 of estrus; Group II — a norgestomet ear implant inserted for 10 days in combination with 1.25 mg PGF₂α given 7 days after insertion and 2,000 IU HCG administered on day 2 of estrus; and Group III — same as II except that 2 mg of GnRH rather than HCG were administered on day 2 of estrus. Blood plasma for radioimmunoassay of progesterone, LH and estradiol was collected from the first day of treatment until 14 days after the end of estrus. Also in March, 6 mares were bled daily from the first day of estrus until subsequent estrus or day 21 (control estrus). Although estrus was detected in all mares, 14 of 18 mares ovulated subsequent to treatments and four of the six control estrus mares ovulated. Only among HCG treated mares was the ovulation rate higher (P < .05) than it was in the control estrus group. The interval from last progesterone injection or norgestomet implant removal to estrus did not differ between treatment groups. Concentrations of estradiol and LH were increased for several days around the time of ovulation and tended to be positively correlated with each other. In the mares that did not ovulate, concentrations of LH and estradiol appeared to be lower than in mares that ovulated. In summary, progestins in combination with PGF₂α and increasing light will synchronize estrus in mares during late winter and HCG will hasten ovulation in some mares.     

Prostaglandin F in the peripheral plasma of the rhesus monkey in normal pregnancy and after the administration of dexamethasone and PGF2α

The concentration of prostaglandin F (PGF) has been measured in the peripheral plasma of normal rhesus monkeys ( ) during the final third of gestation, and in monkeys treated with dexamethasone or PGF₂α after day 145 of pregnancy. Daily administration of PGF₂α (10–15 mg/day im) reliably induced abortion within 3–6 days. However, dexamethasone (8 mg/day im from day 145) had no effect on the length of gestation.The concentration of PGF in the femoral venous plasma of untreated or dexamethasone-treated monkeys was highly variable, both in serial samples taken from the same animal and in samples taken from different animals at the same time of gestation. There was no indication of an effect of dexamethasone treatment on the plasma PGF levels, nor did the concentration of PGF increase during late pregnancy before spontaneous parturition. These results show that the myometrium of the pregnant rhesus monkey is highly sensitive to exogenous PGF₂α during late gestation. However, a significant increase in the peripheral plasma concentration of PGF prior to the onset of labor was not observed.     

Central cardiovascular and thermal effects of prostaglandin F2α in rats

Administration of PGF_2α (0.2–6.4 μg) into the lateral cerebral ventricle (i.c.v.) induced dosedependent increases in blood pressure, heart rate and body temperature in urethane-anaesthetised rats, but had no effect on these parameters when the same dose range was administered intravenously. Peripheral pretreatment with sodium meclofenamate (50 mg/kg s.c.) shifted all the dose-response curves for PGF_2α (i.c.v.) to the left, but indomethacin (50 mg/kg s.c.) did not significantly affect those changes. Central pretreatment with sodium meclofenamate or indomethacin (1.25 mg per rat i.c.v.) failed to modify significantly the effects of centrally administered PGF_2α.The results support previous suggestions that PGF_2α may participate in the central control of the cardiovascular and thermoregulatory systems, and also suggest that there may be differences in the sites and/or modes of action between sodium meclofenamate and indomethacin.     

Reversal of indomethacin blockade of ovulation in gilts by prostaglandins

Prepubertal gilts given 750 IU pregnant mares′ serum gonadotropin (PMSG) followed 72 h later by 500 IU human chorionic gonadotropin (hCG) to induce follicular growth and ovulation fail to ovulate when 10 mg/kg indomethacin (INDO) is injected 24 h after hCG administration. This study examines the effects of administration of exogenous prostaglandins F_2α and E₂ (PGF_2α and PGE₂) alone or in combination, and at various times prior to the expected time of ovulation, on the INDO blockade of ovulation in PMSG/hCG-treated gilts. Occurrence of ovulation was determined by visual observation at laparotomy 48 h after hCG. When 5 mg or 10 mg PGF_2α was injected at each of 38, 40 and 42 h after hCG injection, 63% and 79%, respectively, of preovulatory follicles ovulated. In contrast, injection of 5 mg PGE₂ or 5 mg PGE₂ plus 5 mg PGF_2α induced ovulation in 0% and 24% of preovulatory follicles, respectively. In control groups, 100% of folicles in PMSG/hCG-treated gilts ovulated whereas none did so in PMSG/hCG/INDO-treated animals. These results indicate that administration of PGF_2α can induce ovulation in the PMSG/hCG/INDO-treated prepubertal gilt and suggest that PGE₂ is ineffective and may be antagonistic to PGF_2α in overcoming the ovulation blocking effect of INDO.     

The role of endogenous prostaglandins in the regulation of gastric secretion in rhesus monkeys

Prostaglandins (PG) are known to alter a variety of gastrointestinal functions, but the physiological role of endogenous PG remains unclear. This experiment was designed to evaluate chanes in gastric secretion following both acute and chronic inhibition of PG synthesis with indomethacin (5 mg/kg s.c.). Gastric juice was collected by continuous aspiration in 8 concious chair-adapted male rhesus monkeys following treatment with saline or indomethacin for one or four days. The gastric juice was anzlyzed for H⁺, Na⁺, K⁺ and Cl⁻ concentrations. The amount of soluble mucus in the gastric juice was estimated using Alcian Blue dye binding of acidic glycoproteins and Periodic Acid Schiff reaction with neutral glycoproteins. PG levels were measured in the plasma and in biopsy samples of fundus, antrum and duodenum. Both one and four days of indomethacin significantly (p < 0.05) decreased tissue PG levels in the fundus, antrum and duodenu. Plasma levels of PGF_2α were significantly (p < 0.05) decreased after both one and four days of indomethacin, while PGE₂ and 6-keto PGF_1α were significantly inhibited only after four days of indomethacin. Both acute and chronic inhibition of PG synthesis was accompanied by a decrease in the concentration of sodium and mucus in the gastric juice but by an incrase in the output and concentration of hydrogen ion. These changes suggest a possible mechanism by which endogenous PG play a role in the regulation of gastric secretion and in the protection against gastrointestinal damage.     

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

The ability of human chorionic gonadotropin (HCG) to reduce the luteolytic effect of prostaglandin (PGF_2^α) was demonstrated in cycling ewes. As expected, treatment with 10 mg of PGF_2^α 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 PGF_2^α 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 PGF_2^α because plasma progesterone was reduced when the dose of PGF_2^α was doubled. Whether CL regressed or continued to function after treatment with both HCG and PGF_2^α appeared to depend upon a balance between the positive and negative effects of the two hormones.     

Corpus luteum susceptibility to prostaglandin F2α (PGF2α) luteolysis in hysterectomized prepuberal and mature gilts

The susceptibility of induced corpora lutea (CL) of prepuberal gilts and spontaneously formed CL of mature gilts to prostaglandin F_2α (PGF_2α) luteolysis was studied. Prepuberal gilts (120 to 130 days of age) were induced to ovulate with Pregnant Mare Serum Gonadotropin and Human Chorionic Gonadotropin (HCG). The day following HCG was designated as Day 0. Mature gilts which had displayed two or more estrous cycles of 18 to 22 days were used (onset of estrus = Day 0). Gilts were laparotomized on Day 6 to 9, their CL marked with sterile charcoal and totally hysterectomized. On Day 20, gilts were injected IM with either distilled water (DW), 2.5 mg PGF_2α or 5.0 mg PGF_2α. An additional group of prepuberal gilts was injected with 1.25 mg PGF_2α, a dose of PGF_2α equivalent, on a per kilogram body weight basis, to the 2.5 mg PGF_2α dose given to the mature gilts. The percentages of luteal regression on Day 27 to 30 for mature and prepuberal gilts given DW, 2.5 mg PGF_2α and 5.0 mg PGF_2α were 0.0 vs 4.4, 43.5 vs 96.8 and 47.7 vs 91.6, respectively; the percentage of luteal regression for the prepuberal gilts given 1.25 mg PGF_2α was 75.1. These results indicate that induced CL of the prepuberal gilt were more susceptible to PGF_2α luteolysis than spontaneously formed CL of the mature gilt and that pregnancy failure in the prepuberal gilt could be due to increased susceptibility of induced CL to the natural luteolysin.     

Menstrual cycles in rhesus monkeys (Macaca mulatta) are unaffected by a single dose of the anesthetics ketamine and xylazine administered during the midfollicular phase at laparoscopy

To identify an anesthetic regimen that produces more complete relaxation and analgesia than ketamine hydrochloride (Ketaset®) alone, a combination of ketamine (15 mg/kg body weight) and the hypnotic xylazine (Rompun®, 0.33 mg/kg) was evaluated. Since the desired experimental application required that the anesthetic not interfere with normal hormonal events during the menstrual cycle, this combination administered on day 6 of the cycle was tested to determine whether hormonal surges, incidence of ovulation, or cycle length would be altered relative to the use of ketamine alone. In five of six animals, ketamine plus xylazine had no effect on the occurrence of timely surges of estrogen, luteinizing hormone (LH), or follicle-stimulating hormone (FSH), or on ovulation as determined by the presence of a corpus luteum at laparoscopy and normal serum concentrations of progesterone. There were no significant differences between the cycle during treatment and previous cycles in the same animal for length of the menstrual cycle (26.0 ± 2.3 [5] days; X? ± S.D. [n] or luteal phase (13.4 ± 2.4 [5] days). Likewise, these values did not differ from those of ten control monkeys treated with ketumine only on day 5 or 6 of the cycle (incidence of ovulation, 10/10; cycle length, 27.9 ± 1.8 [10]; luteal phase length, 15.1 ± 1.4 [10], P > 0.05). Patterns of circulating progesterone were not altered by the addition of xylazine anesthesia. These findings indicate that xylazine, given in the midfollicular phase, did not alter ovulatory events or menstrual cycle characteristics in rhesus monkeys. Ketamine plus xylazine apparently provides anesthesia appropriate for laparoscopy.     

Effects of PGF2α and PGF2α, 1–15 lactone on the corpus luteum and on early pregnancy in the rhesus monkey

The effects of prostaglandin (PG)F_2α and PGF_2α, 1–15 lactone were compared in luteal phase, non-pregnant and in early pregnant rhesus monkeys. Animals treated with either PG after pretreatment with human chorionic gonadotropin (hCG) had peripheral plasma progesterone concentrations that were not statistically different from those in animals treated with hCG and vehicle. However, menstrual cycle lengths in monkeys treated with PGF_2α, 1–15 lactone were significantly (P <0.02) shorter than those in vehicle treated animals. In the absence of hCG pretreatment, plasma progesterone concentrations were significantly (P <0.008) lower by the second day after the initial treatment with either PGF_2α or PGF_2α, 1–15 lactone than in vehicle treated monkeys. Menstrual cycle lengths in monkeys treated with either PG were significantly (P <0.04) shorter than those in animals treated with vehicle. There were no changes in plasma progesterone concentrations in early pregnant monkeys treated with PGF_2α, and pregnancy was not interrupted. In contrast, plasma progesterone declined and pregnancy was terminated in 5 of 6 early pregnant monkeys treated with PGF_2α, 1–15 lactone. These data indicate that PGF_2α, 1–15 lactone decreases menstrual cycle lengths in non-pregnant rhesus monkeys. More importantly, PGF_2α, 1–15 lactone terminates early pregnancy in the monkey at a dose which is less than an ineffective dose of PGF_2α.     

The synthesis of Δ2-prostaglandins

The effect of prostaglandin F_2α on ovulation and fertilization was studied in rabbits. The number of ovulation was not affected by subcutaneous injection of PGF_2α but the recovery of ova was significantly decreased when PGF_2α was given either at 12 or 16 h after HCG injection and autopsied 24 h latter. The results suggest that exogenous PGF_2α accelerates ovum transport and expels the eggs prematurely from the female tract and does not impair ovulation or the fertilization processes when given to rabbit at 1 mg/kg B.W.     

In vitro stimulation of prostaglandin synthesis in the rat pancreas by carbamylcholine, caerulein and secretin

Rat pancreas pieces spontaneously released PGE₂ (2.3 ng/100 mg × 45 min) and PGF_2α (7.6 ng/100 mg × 45 min). This release corresponds probably to a neo-synthesis since it was abolished by indomethacin. Carbamylcholine (≥ 10 μM), caerulein (≥ 10 nM) and secretin (≥ 10 nM) stimulated the release of PGE₂ and PGF_2α : the concentrations of stimulators required to increase PGs release were thus much higher than those which trigger enzyme secretion. Atropine specifically inhibited the cholinergic stimulation, whereas indomethacin blocked the stimulatory effects of all secretagogues. Stimulation of PGE₂ and PGF_2α release was reduced in a Ca⁺⁺-free medium, abolished by EGTA and mimicked by the ionophore A23187, underscoring the crucial role of Ca⁺⁺ in the regulation of PGs synthesis by the pancreas. Neither PGE₂ nor PGF_2α stimulated enzyme secretion in this system and indomethacin did not inhibit the secretory effect of carbamylcholine. Increased synthesis of prostaglandins in response to pancreatic secretagogues does not appear to be involved in the process of enzyme secretion.     

Absence of direct effects of prostaglandins on rabbit blastocysts in vitro

A total of 27 monkeys (M. Fascicularis) whose control cycle lengths ranged from 28 to 32 days were used in this study. All the treatments described below started either on day 17 or 18 of the cycle. Six monkeys received daily injections of 20 μg estradiol-17β (E₂) for 5 consecutive days. Although a drop in blood progesterone (P) did occur due to this treatment, no shortening of the luteal phase of the cycle was recorded. Seven monkeys received daily injections of 15 mg PGF_2α (prostaglandin-F_2α) for 4 or 5 days. These monkeys also showed a drop in blood P levels; moreover 5 of these monkeys had vaginal bleeding for 2–3 days starting either on day 19 or 20 of the cycle. This bleeding did not appear to be a normal physiological menstrual flow, since all of the monkeys commenced menstrual flow at the expected time. Four monkeys received daily injections of 10 mg P for 3 days. These monkeys also had normal cycle lengths in spite of the treatment. Finally 9 monkeys received daily injections of 20 μg E₂ for 3 days, and starting on the third day of E₂ treatment these monkeys also received injections of 15 mg PGF_2α for 4 or 5 days. Shortened cycle lengths were recorded in 8/9 monkeys in this group. Six monkeys had 22-day cycles, 2 monkeys had 24-day cycles and the remaining monkey had a cycle length of 26 days. Thus 8/9 monkeys had shortened luteal phases due to sequential treatment of E₂ and PGF_2α. The cycle lengths in all the treatment groups were normal subsequent to treatments. These results provide potentially useful information for further studies in the human as a method of contraception.