Sperm output and serum testosterone in rabbits given prostaglandin F2α or E2

Two experiments were conducted, the first to compare sperm output and the second to determine serum testosterone in rabbits given PGF₂α or PGE₂. In the first, six rabbits were ejaculated twice each Monday, Wednesday and Friday for 5 weeks. Each rabbit was given subcutaneously (sc) each of the following treatments five times: 1) saline, 2) 5 mg PGF₂α and 3) 5 mg PGE₂. Treatments were given, half at 4 hr and half at 2 hr before first ejaculations. Both PGF₂α and PGE₂ caused increased (50% and 84%) sperm content of first ejacula, without significantly altering characteristics of second ejacula. The extra sperm in first ejacula was a function of increased sperm density, because seminal volume was unaltered.In the second experiment, 15 rabbits were bled at 0.5-hr intervals for 9 hr and given (sc): 1) saline at 1 and 3 hr (n=4), 2) 2.5 mg PGF₂α at 1 and 3 hr (n=4), 3) 2.5 mg PGE₂ at 1 and 3 hr (n=4) or 4) 5 mg PGF₂α at 1 hr after the onset of blood sampling. In saline-treated controls, episodic surges of testosterone occurred on the average every 5 hours. After the injection of 2.5 or 5.0 mg PGF₂α, serum testosterone began to rise at 0.5 hr, peaked (8 to 13 ng/ml) at 1 hr and approached a nadir (0.5 ng/ml) within 4 hours. The second injection of 2.5 mg PGF₂α failed to significantly affect serum testosterone. PGE₂ treatment was followed by significantly depressed serum testosterone; only 1 of these 4 rabbits had any surge of testosterone for the 8 hr after treatment. In conclusion, PGF₂α and PGE₂ both increased sperm output, but PGF₂α increased serum testosterone while PGE₂ depressed serum testosterone. Thus, the sperm output effect of these prostaglandins probably is independent of the acute changes in testosterone secretion.     

Luteolysis, estrus and ovulation, and blood prostaglandin F after intramuscular administration of 15, 30 or 60 mg prostaglandin F2α

During diestrus in three consecutive estrous cycles, each of six heifers was given (im) 30 mg, 15 mg (twice at 6-hr intervals) and 60 mg prostaglandin F_2α (PGF_2α) tham salt. Neither the decline in blood progesterone, the increase in blood estradiol, the duration or the peak of the LH surge, the interval to onset of estrus, nor the interval to ovulation was affected significantly by dose of PGF_2α. Thus, relative to that after 30 mg PGF_2α im, two injections of 15 mg at 6-hr intervals or 60 mg PGF_2α did not hasten luteolysis. Thirty mg was an ample im dose of PGF_2α to cause luteolysis. Regardless of im dose of PGF_2α, blood PGF peaked at about 6.0 ng/ml within 10 minutes and returned to basal values (<1.0 ng/ml) within 90 minutes. In another trial, after a single iv injection of 5 mg PGF_2α, blood PGF peaked (25 ng/ml) within 5 minutes and returned to basal values within 15 minutes. During a 30-minute infusion (0.5 mg/minute) of PGF_2α, blood PGF plateaued at 29.5 ng/ml with a metabolic clearance rate of 17.0 liters per minute.     

Effect of PGF2α on progesterone secretion and adenylate cyclase activity in ovine luteal tissue

Ovine luteal slices were used to study the effects of prostaglandins (PG) F₂α on luteinizing hormone (LH)-stimulated secretion of progesterone and adenylate cyclase activity. The accumulation of progesterone in incubation medium and adenylate cyclase activity was similar after incubation of luteal slices with Medium 199 alone or Medium 199 containing PGF₂α (250 ng/ml) for 3 hr. Addition of luteinizing hormone (LH; 100 ng/ml) resulted in a 2–3 fold increase in both the rate of progesterone accumulation and adenylate eyclase activity by 3 hr. When luteal slices were incubated in the presence of both LH and PGF₂α the rates of progesterone accumulation and adenylate cyclase activity were identical to those in flasks containing LH alone after 1 hr; however, after 3 hr both LH stimulated progesterone accumulation and adenylate cyclase activity were inhibited to levels similar to those observed in control slices.In a second experiment, after 60–120 min of exposure to PGF₂α the rate of progesterone accumulation in the medium was not different from that in untreated control slices. In addition, after this experiment the luteal slices were homogenized and the basal, sodium fluoride, LH, isoproterenol (ISO) and PGE₂ sensitive adenylate cyclase activities were determined to evaluate the hormonal specificity of the negative effect of the pretreatment with PGF₂α. Both LH and ISO stimulated adenylate cyclase activities were reduced after PGF₂α pretreatment. However, fluoride ion stimulated adenylate cyclase activity was not significantly effected by PGF₂α pretreatment and PGE₂ sensitive adenylate cyclase was effected only slightly.     

Blood LH after PGF2α in diestrous and ovariectomized cattle

Two experiments were conducted to determine whether the increased serum LH which occurs within 12 hr after a luteolytic dose of PGF_2α is dependent upon changes in progesterone or estradiol secretion. In the first experiment, exogenous progesterone abolished the increase in serum LH caused by a subcutaneous injection of 25 mg PGF_2α in diestrous heifers, but not in ovariectomized heifers. In the second experiment, progesterone pessaries were removed at 6 hr after a subcutaneous injection of 25 mg PGF_2α. LH remained at pre-PGF_2α values while the pessaries were in place, but began to increase within 1 hr after they were removed. Blood estradiol also remained at pre-PGF_2α values until the pessaries were removed, and began to increase at 2 hr after pessary removal. We conclude that the increase in serum LH within 12 hr after PGF_2α treatment in diestrous cattle is dependent upon withdrawal of progesterone; it is not due to increased serum estradiol.     

Effect of prostaglandin F2α on uterine or ovarian secretion of prostaglandins E and F2α in vivo in 90–100 day hysterectomized, intact or ovariectomized pregnant ewes

Vehicle or 8 or 16 mg of PGF_2α per 58 kg body weight was given intramuscularly to intact, hysterectomized or ovariectomized 90–100 day pregnant ewes in three separate experiments. Both doses of PGF_2α increased PGF_2α in ovarian venous plasma compared with controls at 72 hr post treatment in intact (P≤0.05) but did not in hysterectomized (P≥0.05) 90–100 day pregnant ewes. Concentrations of PGE in ovarian venous blood of intact ewes did not differ (P≥0.05) between treatment groups and were equivalent to concentrations of PGE determined in uterine venous plasma. PGE was decreased in ovarian venous plasma by PGF_2α in hysterectomized ewes (P≤0.07). PGE in uterine venous plasma averaged 6 ng/ml over the 72-hr treatment period in intact and ovariectomized 90–100 day pregnant ewes and was 12 fold greater (P≤0.05) than PGF_2α which averaged 500 pg/ml in uterine venous plasma. Both PGF_2α and PGE increased (P≤0.05) by 64 hr in uterine venous plasma of the 8 mg PGF_2α — treated intact pregnant ewes. A significant quadratic increase (P≤0.05) was observed for PGF_2α and PGE in the vehicle and both PGF_2α treatment groups of intact ewes at the end of the 72-hr sampling period. It is concluded that the uterus and ovaries secrete significant quantities of PGE but little PGF_2α during midgestation. In addition, PGF_2α increased uterine secretion of PGE . PGE may be a placental stimulator of ovine placental secretion of progesterone or PGE may protect placental steroidogenesis from actions of PGF_2α.     

Synchronization of preovulatory LH surges after PGF2 alpha in beef cattle: the effects of D-ala-GnRH and testosterone benzoate.

Three successive periods of estrus were induced by PGF_2α administration in beef cows and heifers. The magnitude, duration and timing of preovulatory LH surges were compared in animals subjected to each of the following treatments during one of the periods of estrus following PGF_2α injection: a) no treatment, b) 50 g Ayerst D-ala-GnRH (AY25205) im at 64 h or c) 3 mg testosterone benzoate im at 48 h. Spontaneous LH surges, 15 – 40 ng/ml in magnitude and 8 – 12 h in duration occurred between 60 and 104 h after PGF_2α. Testoster-one benzoate suppressed and appeared to delay LH surges in 2 of 3 trials. D-ala-GnRH effectively induced preovulatory surges which were considerably greater in magnitude but slightly shorter in duration than spontaneous surges. The data suggest that D-ala-GnRH administered 64 h after the luteolytic dose of PGF_2α is an effective means of synchronization of preovulatory LH surges. Further, this treatment may be a valuable aid in improving fertility to a single insemination in PGF_2α-synchronized beef cows.     

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection

Adult male rhesus were treated with PGE₂, PGF_2α or the 13,14-dihydro-15-keto metabolite of PGE₂ in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF_2α was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE₂ was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE₂ or PGF_2α can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.     

Failure of exogenous LH to prevent PGF2α-induced luteolysis in beef cows

Henderson and McNatty (Prostaglandins 9:779, 1975) proposed that LH from the preovulatory LH surge attached to receptors on luteal cells and that this attachment might protect the early corpus luteum from PGF_2α induced luteolysis. To test this hypothesis, experiments were performed on heifers at day 10–12 of the cycle. Both jugular veins were catheterized and infusions of either saline (0.64 ml/min) or LH-NIH-B9 (10 μg/min; 0.64 ml/min) were given. Saline infusions were from 0–12 h; LH infusions were for 10 h and were preceded by a 2 h saline infusion. All animals were given 25 mg PGF_2α im at 6 h (6 h into the saline infusion and 4 h into the LH infusion). Blood samples were taken at 0.5 h, 1 h and 4 h intervals from 0–12, 13–18 h and 22–24 h respectively. Serum was assayed for LH and progesterone by radioimmunoassay methods. Two animals received saline and two received LH in each experiment. Eact treatment was replicated 6 times. LH infusion resulted in a mean serum LH of 57 ng/ml compared to 0.90 ng/ml in saline infused animals. This elevation of LH did not alter PGF_2α induced luteolysis as indicated by decline in serum progesterone. This experiment does not support the hypothesis that the newly formed corpus luteum is resistant to PGF_2α because of protection afforded by the protestrus LH surge.     

Increased sperm output of rabbits and bulls treated with prostaglandin F2α

Seven rabbits were ejaculated four times once weekly, and saline or 2.5 mg PGF_2α tromethamine salt was injected sc at 4 and 2 hours or at 8 and 4 hours before ejaculation. First ejacula taken at 2 hours after the second injection of PGF_2α contained 150% more (P.07) sperm than those after injections of saline. The comparable difference (60%) at 4 hours after PGF_2α was not significant. PGF_2α did not influence sperm output in second, third or fourth ejacula. After 28 daily sc injections of 5 mg PGF_2α in another experiment, the fertility of four treated rabbits was as high as that for four controls. Without sexual preparation in seven bulls, im injections of 40 or 80 mg PGF_2α 30 minutes before ejaculation resulted in 33% greater (P<.05) sperm output than that after injection of 0, 7 or 20 mg PGF_2α, but the highest sperm output after PGF_2α was 30% less (P<.05) than that after sexual preparation in the same bulls. We conclude that injections of PGF_2α result in increased sperm output in ejacula taken without sexual preparation within 2 hours in rabbits and in bulls.     

Effect of repeated sampling on concentrations of testosterone,LH and prolactin in blood of yearling angus bulls

Blood was collected at intervals of 29 to 31 min for 5 hr from six Angus bulls (15 mo of age) unaccustomed to capture, restraint and jugular venipuncture (stress) to evaluate temporal changes in certain hormones. Concentrations of testosterone and luteinizing hormone (LH) but not prolactin were decreased significantly after the first hour. Testosterone in plasma decreased (P < .01) about 11-fold between 0 hr and 5 hr (9.9 ± 1.7 to .85 ± .16 ng/ml) as described by equation log_e testosterone = log_e 2.4649 ? .5266 hr (r = .83; P < .01). Concentrations of LH in plasma remained low after the first hour and those of prolactin were high at all times and varied significantly only among bulls (27 ± 6 to 84 ± 14 ng/ml). Testosterone but not LH was measured with equal repeatability among duplicate measurements either in whole blood or plasma but its average concentration in whole blood was 66% that of plasma. This study demonstrated that sequential collection of blood from bulls unaccustomed to capture and restraint cannot be used to evaluate normal temporal variations in concentrations of testosterone.     

Interactions of prostaglandins with subpopulations of ovine luteal cells. II. Inhibitory effects of PGF2α and protection by PGE2

Purified preparations of ovine large luteal cells were utilized in a series of experiments to test the effects of prostaglandins (PG) E₂ abd F₂α on cell morphology, viability and secretion of progesterone. Luteal cells were allowed to attach to culture dishes overnight before experiments. In the first series of experiments incubation of large steroidogenic cells with PGF₂α for 6 hr resulted in morphological changes including a retraction of the cell cytoplasm and apparent extrusion of cytoplasmic components which became more pronounced after 12 hr. In a second series of experiments, PGF₂α decreased and PGE₂ increased progesterone accumulation in media after 6 hr when media were not replaced during the incubation period, while progesterone accumulation was not different than that observed in control dishes when both prostaglandins were present. Hourly replacement of the media negated the inhibitory effects of PGF₂α but had no effect on the stimulated secretion of progesterone induced by PGE₂. Finally, in incubations without media replacement, PGF₂α induced a dose-dependent decrease in progesterone accumulation while PGE₂ elicited a biphasic response with progesterone secretion increasing from 0.1 ng/ml to maximal levels at 10 ng/ml followed by a dose-dependent decrease at 100 and 1000 ng/ml. These data are compatible with the hypotheses that: 1) luteolysis is initiated, at least in part, by an action of PGF₂α on large luteal cells; and 2) the embryonic signal from the pregnant uterus which rescues the ovine corpus luteum may be PGE₂.     

The excretion of prostaglandin F2α in milk of cows

Prostaglandin F_2α (PGF_2α) was measured by immunoassay in plasma and milk of four cows (six experiments). After 30 mg PGF_2α im, plasma PGF_2α peaked at 15 minutes (2.4 ± 0.7 ng/ml) and declined toward basal values by 3 hours; maximum milk PGF_2α (0.91 ± 0.12 ng/ml) occurred at 1 hour. The average excretion rate in milk was 2.9 μg/day 0.9 μg (0.003%) of which was due to the 30 mg PGF_2α injected. In six non-pregnant control cows, daily changes of milk PGF_2α and progesterone were not consistently related.     

An intra-corpus luteum site for the luteolytic action of prostaglandin F2α in the rhesus monkey

It has not been possible to demonstrate prostaglandin F₂α (PGF₂α) participation in primate luteolysis under conditions of systemic administration or of acute intraluteal injection. These study designs were hampered by the short biological half-life in the first instance and brevity of administration in the latter. In this study, luteolysis has resulted from chronic, intraluteal delivery of PGF₂ α. Using the Alzet osmotic pump-cannula system, normally cycling rhesus monkeys were continuously infused, until menses occurred, with PGF₂ α (10 ng/1/hr) directly into the corpus luteum (CL, n=6), into the stroma of the ovary bot bearing the corpus luteum (NCL, n=3), or subcutaneously (SC, n=5). An additional 5 monkeys received vehicle (V) into the corpus luteum. All experiments commenced 5–7 days after the preovulatory estradiol surge. Luteal function was assessed by the daily measurements of plasma progesterone, estradiol, and LH. Intraluteal PGF₂α caused premature functional luteolysis in all monkeys, as reflected by a highly significant decline in circulating progesterone and estradiol and the early onset of menstruation, when compared to the other groups. V, NCL, and SC infusions had no effect on either circulating steroid levels or luteal phase lengths. None of the experimental groups showed any change in plasma LH concentrations. These are the first data to indicate that PGF₂α can induce functional luteolysis in the primate, and the site of action appears to be the corpus luteum.     

Effect of in vivo prostaglandin treatment on H-PGF2α uptake in hamster corpora lutea

Pregnant hamsters were administered (SC) prostaglandin or vehicle on the morning of the 4th day of pregnancy. Serum progesterone was significantly depressed (p<.01) at 0.5, 2, and 6 hours after treatment with 100 μg PGF_2α. Serum progesterone levels were unchanged 2 hours and 6 hours after treatment with 100 μg PGF_2β and 2 hours after treatment with 1 mg PGF_2β. Progesterone levels were depressed to less than 1 ng/ml 6 hours after treatment with 1 mg PGF_2β. The specific uptake of ³H-PGF_2α in whole hamster corpora lutea was significantly depressed 2 hours and 6 hours following 100 μg PGF_2α treatment. A 15% depression in specific uptake occurred 0.5 hour post-treatment. Treatment with 100 μg PGF_2β resulted in no change. Administration of 1 mg PGF_2β resulted in depressed ³H-PGF_2α uptake at both 2 and 6 hours post-treatment.Prostacyclin (PGI₂) treatment resulted in no change in either ³H-PGF_2α specific uptake or serum progesterone 2 hours after 100 μg treatment SC. These parameters were both reduced approximately 30% 6 hours post-treatment. Treatment with 6-keto-PGF_1α resulted in a complete lack of measurable ³H-PGF_2α uptake and serum progesterone levels less than 1 ng/ml at both 2 and 6 hours after treatment with 1 mg SC.     

Effect of prostaglandin F2α on ovarian and pituitary function in the mid-luteal phase

The effects of PGF_2α infusion in a dose of 25 μg/min for 5 hours on serum levels of estradiol-17β, progesterone, LH, FSH, TSH and prolactin, and on the pituitary hormone responsiveness to LRH and TRH were studied in 10 apparently healthy cycling women in the mid-luteal phase. No systematic alteration was seen in the pituitary and ovarian hormone levels during PGF_2α infusion, and the pituitary hormone responses to releasing hormones were unaffected. Ovarian steroid production increased in response to increased gonadotropin levels after LRH injection during PGF_2α administration. These results confirm that PGF_2α is not luteolytic in humans and no apparent relationship between PGF_2α and pituitary hormone secretion exists.     

Effects of dibuturyl cAMP, LHRH, and aromatase inhibitor on simultaneous outputs of prostaglandin F2α, and 13,14-dihydro-15-keto-prostaglandin F2α by term placental explants

Explants from term human placentas were maintained in culture with daily changes of medium. Daily output of PGF_2α and PGFM¹ decreased during the course of the incubation. Addition of 4 μg/ml DHEAS or 67 μg/ml LDL cholesterol had no effect on output of PGF_2α or PGFM. Addition of 1.6, 3.2, or 6.4 μg/ml of LHRH to the culture plates had no effect on output of PGFM or PGF_2α, but LHRH increased hCG output. Dibutyryl cAMP (1mM, 2mM, and 4mM) increased output of PGF_2α, PGFM, and hCG. Aromatase inhibitor decreased hCG output, but it was without effect on output of PGF_2α, or PGFM. Significant correlations were demonstrated between progesterone, PGFM, PGF_2α, and hCG, suggesting that PGF_2α originates in the syncytiotrophoblast cell. The ability of LHRH to stimulate output of hCG but not PGF_2α while dbcAMP stimulated both suggests that either PGF_2α and hCG arise in different cells or that LHRH does not act through cAMP.     

Failure of LH and/or prolactin to prevent PGF2α-induced luteolysis of ovine corpora lutea

Infusions of phosphate buffered saline, LH (4 μg/min or 14 μg/min), prolactin (42 μg/min) or LH (4 μg/min) plus prolactin (42 μg/min) for 12 hr did not prevent luteolysis following intramuscular injections of prostaglandin F₂α-tham salt two and six hr after beginning the infusion. Likewise, these treatments did not delay luteolysis since a similar rate of decline in peripheral plasma progesterone occurred in all groups. It was concluded that elevation of serum concentrations of LH and prolactin to high levels had no effect on PGF₂α-induced luteolysis on day 8 following induced ovulation.     

Prostaglandin (PG) analysis in urine of humans and rats by different radioimmunoassays: Effect on PG-excretion by PG-synthetase inhibitors, laparotomy and furosemide

Thw radioimmunological (RIA) determination of prostaglandin (PG) E₂ and of PGF_2α in urine humans and rats is described in detail. After extraction and chromatography PGE₂ was determined by using a PGE specific antibody or by using either PGB or PGF_2α specific antibodies after the respective conversion procedures. The three different RIA procedures were compared to each other. PGF_2α was determined by a specific antibody to PGF_2α. Basal excretion of PGE₂ and of PGF_2α in healthy women on free diet was 9.3 ng/hour ± 0.96 and 18.3 ng/hour ± 2.5 respectively. Furosemide increased the excretion of PGE₂ and of PGF_2α in humans significantly, while PG-excretion rates decreased on indomethacin. In rat urine PGE₂ and PGE_2α increased markedly from 46.2 pg/min ± 9.3 and 27 ± 3.4 to 253.8 ± 43.3 and 108 ± 12.6 pg/min (per one kidney) in the anesthetized-laparotomized animal. This increase was abolished after giving two different PG synthetase inhibitors.     

Mating increases plasma levels of prostaglandin F2α in female garter snakes

Plasma levels of prostaglandin F_2α (PGF_2α) in female red-sided garter snakes (

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) were measured at intervals after mating or exposure to males. PGF_2α levels increased significantly within 15 minutes of mating and peaked 6–24 hr after mating. Females that did not mate, but received similar amounts of male courtship, had levels of PGF_2α significantly lower than those of females that mated. These results extend previous findings that unmated female garter snakes injected with PGF_2α exhibit sexual behavior characteristics of females that have mated. Together these data indicate that female garter snakes elaborate PGF_2α in response to stimuli associated with mating and that PGF_2α has a functional role in inducing post-mating declines in sexual behavior of this species.     

Effects of prostaglandins E1 and F2α on serum luteinizing hormone concentration and on some sexual functions in male rabbits

PGE₁(50μg/animal) and PGF_2α (250 μg/animal) caused a transient in serum LH at 5 min after injection. PGE₁ (250 μg/animal) had a biphasic effect on serum LH. A small peak was obtained at 5 min, and a second, larger peak at 60 min after injection. It is suggested that the first peak is a result of the stress associated with injection of the PGs, whereas the second peak represents a physiological effect of PGE. Subcutaneous injection of PGE₁ (1 mg in arachis oil b.i.d.) for 10 days did not affect the concentration of LH in serum, the function of the accessory sexual glands or the sexual activity. PGF_2α, given at the same dose and in the same manner, increased the sexual activity but left all other variables unaffected. The pituitary responsiveness to LH-RH was unaltered by the treatment with PGE₁ and PGF_2α.