共查询到20条相似文献,搜索用时 31 毫秒
1.
H. D. Hafs T. M. Louis R. J. Waters J. N. Stellflug N. B. Haynes 《Prostaglandins & other lipid mediators》1974,8(5):417-422
Seven rabbits were ejaculated four times once weekly, and saline or 2.5 mg PGF2α 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 PGF2α contained 150% more (P.07) sperm than those after injections of saline. The comparable difference (60%) at 4 hours after PGF2α was not significant. PGF2α did not influence sperm output in second, third or fourth ejacula. After 28 daily sc injections of 5 mg PGF2α 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 PGF2α 30 minutes before ejaculation resulted in 33% greater (P<.05) sperm output than that after injection of 0, 7 or 20 mg PGF2α, but the highest sperm output after PGF2α was 30% less (P<.05) than that after sexual preparation in the same bulls. We conclude that injections of PGF2α result in increased sperm output in ejacula taken without sexual preparation within 2 hours in rabbits and in bulls. 相似文献
2.
Six mature stallions were used to test the effect of prostaglandin F2α (PGF2α) on sperm production and seminal characteristics. Semen was collected from each stallion twice weekly 1 hr following a 10 mg intramuscular injection of PGF2α or a sham injection. A switchback design was used so that three stallions received PGF2 and three served as controls during the first 9 weeks (period 1). Threatment regimens were reversed during the second 9 weeks (period 2). Treatment of stallions with PGF2α resulted in an increase (/prmP<.05) in gel free seminla voume and a decrease in sperm cell concentration. Total spermatozoa, sperm cell motility, and percentage of primary and secondary sperm abnormalities or ejaculates were not significantly affected by treatment of stallions with PGF2α before semen collection. All treated stallions exhibited a pronounced sweating response to the drug. During the experiment, two of the six stallions masturbated within 20 to 30 minutes after PGF2α treatment without achieving an erection. 相似文献
3.
C.H. Spilman D.C. Beuving A.D. Forbes F.A. Kimball 《Prostaglandins & other lipid mediators》1977,14(3):477-488
The effects of prostaglandin (PG)F2α and PGF2α, 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 PGF2α, 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 PGF2α or PGF2α, 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 PGF2α, and pregnancy was not interrupted. In contrast, plasma progesterone declined and pregnancy was terminated in 5 of 6 early pregnant monkeys treated with PGF2α, 1–15 lactone. These data indicate that PGF2α, 1–15 lactone decreases menstrual cycle lengths in non-pregnant rhesus monkeys. More importantly, PGF2α, 1–15 lactone terminates early pregnancy in the monkey at a dose which is less than an ineffective dose of PGF2α. 相似文献
4.
L.A. Reichard H.D. Hafs N.B. Haynes R.J. Collier T.E. Kiser M.S. McCarthy 《Prostaglandins & other lipid mediators》1978,16(1):135-142
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. 相似文献
5.
C. H. Spilman 《Prostaglandins & other lipid mediators》1974,7(6):465-472
Oviductal motility was measured in the isthmus of ovariectomized New Zealand rabbits. The effects of estradiol and progesterone on spontaneous motility and on the response of the oviduct to exogenously administered prostaglandin E1 (PGE1) and PGF2α were determined. Estradiol treatment significantly increased both the amplitude (P<0.05) and frequency (P<0.01) of spontaneous contractions. The amplitude of spontaneous activity was less following progesterone treatment than following estradiol treatment (P<0.05). Progesterone treatment increased the duration of oviduct response to PGE1 (P<0.05). Estradiol treatment had no effect on the response to PGE1. Increased oviductal activity caused by PGF2α lasted significantly (P<0.01) longer in ovariectomized, untreated animals than in ovariectomized animals treated with estradiol or progesterone. Progesterone was more effective than estradiol in decreasing the duration of the response to PGF2α. These effects of steroid hormones on the responsiveness of the oviduct to PGE1 and PGF2α could contribute to the physiological control of egg transport. The nadir of ovarian hormone influence, as in the recently ovariectomized animals and as occurs immediately after ovulation, is associated with a high responsiveness of the oviduct to PGF2α. This could effectively increase isthmic occlusion and prevent the eggs from passing through the oviduct prematurely. The gradual increase in ovarian estradiol and progesterone secretion during the 3
days following coitus could result in decreased responsiveness to PGF2α and increased responsiveness to PGE1. These changes might cause relaxation of isthmic tone and allow movement of eggs through the isthmus into the uterus. 相似文献
6.
J.L. Black C.L. Armour K.S. Vincenc P.R.A. Johnson 《Prostaglandins & other lipid mediators》1986,32(1)
Prostaglandins may be implicated in the bronchoconstriction which occurs in asthma. Prostaglandins F2α (PGF2α and D2 (PGD2) have been reported to produce bronchoconstriction in asthmatic subjects in vivo and PGF2α cotnracts human isolated airway smooth muscle. We examined the relative efficacy and potency of PGF2α and PGD2 on human bronchial spiral strips taken from 6 patients at thoracotomy. PGF2α had greater efficacy than PGD2. The mean % Tmax (percentage of maximal contractile response) ± s.e. mean were 84 ± 7 and 54 ±7 respectively (P < 0.05). PGF2α (mean pD2 ± s.e. mean = 6.39 ± 0.6) tended to be more potent than PGD2 (5.68 ± 0.2). Since, in vivo, PGD2 has greater efficacy and potency than PGF2α, our results suggest that the in vivo effect of these prostaglandins does not result solely from an action on airway muscle. 相似文献
7.
To test the hypothesis that abnormal prostaglandin reactivity may be a characteristic of essential hypertension, cardiovascular responses to prostaglandin F2α (PGF2α) were measured in young spontaneously hypertensive (SHR) and Wistar normotensive rats (NR). PGF2α(1 sec injection; 50 l/100 g.; .05, .5, 5, 50 g salt/kg) was injected retrograde into the femoral artery. Maximum changes were measured with respect to: 1) four different diameter categories of cremaster muscle arterioles, 2) mean arterial pressure (MAP), 3) pulse pressure (PP) and 4) heart rate. PGF2α at 5 and 50 g/kg significantly increased NR and SHR blood pressure. SHR MAP increased significantly more than NR MAP with the 50 g dose (P <. 001). PGF2α increased NR PP at the 50 g/kg dose and increased SHR PP at the .5, 5 and 50 g/kg dose. SHR PP response was significantly greater than that of the NR with the .5, 5 and 50 g/kg dose (P < .05, .01, .001 respectively). The mean SHR arteriolar constriction was greater than that of NR with the 50 g dose. The only change in heart rate was a 3% decrease from control in both NR and SHR during the pressor response to 50 g/kg. These results show an increased cardiovascular reactivity to PGF2α in SHR and may further suggest prostaglandin involvement in hypertensive disease. 相似文献
8.
Y.S. Weems D.L. Vincent K.D. Nusser Y. Tanaka K. Miller-Patrick K.S. Ledgerwood C.W. Weems 《Prostaglandins & other lipid mediators》1993,46(3)
Vehicle or 8 or 16 mg of PGF2α 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 PGF2α increased PGF2α 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 PGF2α 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 PGF2α which averaged 500 pg/ml in uterine venous plasma. Both PGF2α and PGE increased (P≤0.05) by 64 hr in uterine venous plasma of the 8 mg PGF2α — treated intact pregnant ewes. A significant quadratic increase (P≤0.05) was observed for PGF2α and PGE in the vehicle and both PGF2α 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 PGF2α during midgestation. In addition, PGF2α 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 PGF2α. 相似文献
9.
H. Karppanen Anna-Leena Sirn Alice Eskeli-Kaivosoja 《Prostaglandins & other lipid mediators》1979,17(3):385-394
Administration of PGF2α (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 PGF2α (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 PGF2α.The results support previous suggestions that PGF2α 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. 相似文献
10.
G.J. Wiepz M.C. Wiltbank S.B. Kater G.D. Niswender H.R. Sawyer 《Prostaglandins & other lipid mediators》1993,45(2)
When ovine large luteal cells are placed in culture and exposed to PGF2α, there is a rapid and sustained increase in the concentration of free intracellular calcium which is believed to play a major role in the luteolytic and cytotoxic effects of PGF2α. Since administration of exogenous PGE2 can prevent spontaneous and PGF2α-induced luteolysis in vivo, and the cytotoxic effects of PGF2α on large luteal cells in vitro, the objective of this study was to determine if one mechanism by which PGE2 acts is to attenuate increases in free intracellular calcium induced by PGF2α. At concentrations of 10 nM or greater, PGF2α caused a significant and sustained increase in free intracellular calcium in large luteal cells. Similarly, PGE2 also induced increases in free intracellular calcium but required doses 20-fold greater than PGF2α. When PGE2 (1, 10 or 100 nM) was incubated with PGF2α (100 nM) increases in free intracellular calcium induced by PGF2α were attenuated (P<0.05) when measured 5 min, but not at 30 min, after initiation of treatment. The observed decrease in the concentration of free intracellular calcium at 5 min in response to PGF2α was the result of fewer cells responding to PGF2α. In addition, the concentrations of free intracellular calcium attained in the cells that did respond was reduced 25% compared to cells treated with PGF2α alone. Thus, part of the luteal protective actions of PGE2 appears to involve an inhibition of the early (5 min) increase in free intracellular calcium induced by PGF2α. 相似文献
11.
J. N. Stellflug T. M. Louis H. D. Hafs B. E. Seguin 《Prostaglandins & other lipid mediators》1975,9(4):609-615
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 F2α (PGF2α) 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 PGF2α. Thus, relative to that after 30 mg PGF2α im, two injections of 15 mg at 6-hr intervals or 60 mg PGF2α did not hasten luteolysis. Thirty mg was an ample im dose of PGF2α to cause luteolysis. Regardless of im dose of PGF2α, 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 PGF2α, 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 PGF2α, blood PGF plateaued at 29.5 ng/ml with a metabolic clearance rate of 17.0 liters per minute. 相似文献
12.
The mechanism of stimulatory and inhibitory action of PGF2α on ovarian steroidogenesis both under
and
conditions has been studied in the pseudo-pregnant rabbits. Short term incubation of the ovaries with PGF2α (2.82 × 10−5M) resulted in an increased synthesis of progesterone and 20α-OH P. The addition of PGF2α in the medium and further incubation of the ovaries obtained from rabbits that had been constantly infused with PGF2α (0.5 μg/min.) for two hours resulted in increased synthesis of these progestins. The ratio of progesterone to 20α -OH P was also enhanced under these conditions and thus supported the luteotropic action of small doses of PGF2α under short term incubations. However, as the amount of PGF2α infused was increased to 5 μg/min., the addition of PGF2α under
conditions strikingly decreased the production of these progestins. The ratio of progesterone to 20α -OH P was also decreased and thus was indicative of luteolytic action of higher doses of PGF2α. High doses of PGF2α (5.64 × 10−4M) failed to I cause any significant change in the progestin synthesis under short term incubation. These results thus suggest that the luteotropic and luteolytic action of PGF2α in the luteinized rabbit ovary is dose and time dependent. 相似文献
13.
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 PGF2α. Serum progesterone levels were unchanged 2 hours and 6 hours after treatment with 100 μg PGF2β and 2 hours after treatment with 1 mg PGF2β. Progesterone levels were depressed to less than 1 ng/ml 6 hours after treatment with 1 mg PGF2β. The specific uptake of 3H-PGF2α in whole hamster corpora lutea was significantly depressed 2 hours and 6 hours following 100 μg PGF2α treatment. A 15% depression in specific uptake occurred 0.5 hour post-treatment. Treatment with 100 μg PGF2β resulted in no change. Administration of 1 mg PGF2β resulted in depressed 3H-PGF2α uptake at both 2 and 6 hours post-treatment.Prostacyclin (PGI2) treatment resulted in no change in either 3H-PGF2α 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-PGF1α resulted in a complete lack of measurable 3H-PGF2α uptake and serum progesterone levels less than 1 ng/ml at both 2 and 6 hours after treatment with 1 mg SC. 相似文献
14.
Prostaglandin F2α (PGF2α) has been shown to be an effective stimulant of hepatic bile flow producing a specific chloride rich bile. Subsequent evaluation by radioimmunoassay has shown that prostaglandin F compounds are present in relatively large amounts in canine hepatic bile. This study evaluates the effect of PGF2α administration and of prostaglandin synthetase inhibition by aspirin and indomethacin on bile flow and radioimmunoassayable prostaglandin F (iPGF) secretion. Chronic, canine bile fistula preparations were utilized and the enterohepatic circulation was maintained by intravenous bile salts. Bile volume and composition were evaluated by standard techniques as well as bile PGF concentration by radioimmunoassay during bile salt infusion and during bile salt and PGF2α, aspirin and indomethacin infusion in varying doses. Both aspirin and PGF2α were potent stimulatns of hepatic bile flow with aspirin producing a chloride rich bile similar to that produced by PGF2α. PGF2α produced dose related increases in bile iPGF concentration and output indicating that as the systemic concentration increases during infusion of PGF2α the lipid appears in bile. Aspirin in the highest dose administered, decreased iPGF concentration in bile while output was unchanged. Indomethacin was ineffectual in consistently altering bile flow or iPGF secretion. This study demonstrates that iPGF is present in canine bile, that its concentration can be altered by prostaglandin infusion while prostaglandin synthetase inhibition has minimal effects on bile iPGF secretion. 相似文献
15.
Twenty crossbred gilts with at least 2 consecutive estrous cycles of 18 to 21 days in length were used to study the effects of prostaglandins E2 and F2α (PGE2 and PGF2α) on luteal function in indomethacin (INDO) treated cycling gilts. Intrauterine and jugular vein catheters were surgically palced before day 7 of the treatment estrous cycle and gilts were randomly assigned to 1 of 5 treatment groups (4/groups). With exception of the controls (Group I) all gilts received 3.3 mg/kg INDO every 8 h, Groups III, IV and V received 2.5 mg PGF2; 2.5 mg PGF2α + 400 μg PGE2 every 4 hr, or 400μg PGE2 every 4 h, respectively. All treatments were initiated on day 7 and continued until estrus or day 23. Jugular blood for progesterone analysis was collected twice daily from day 7 to 30. Estradiol-17β (E2-17β) concentrations were dtermined in samples collected twice daily, from 2 d before until 2 d following the day of estrus onset. When compared to pretreatment values, estrous cycle length was unaffected (P>0.05) in Group I, prolonged (P<0.05) in Groups II, IV and V; and shortened (P<0.05) in Group III. The decline in plasma progesterone concentration that normally occurs around day 15 was unaffected (P>.05) in Group I; delayed (P<0.05) in Groups II, IV and V; and occurred early (P<0.05) in Group III. Mean E2-17β remained high (31.2 ± 4.9 to 49.3 ± 3.1 pg/ml) in Groups III and IV, while the mean concentrations in Groups III and V varied considerably (17.0 ± 2.0 to 52.2 ± 3.5 pg/ml). The results of this study have shown that PGE2 will counteract the effects of PGF2α in INDO treated cycling gilts. The inclusion of PGF2α appeared to either stimulate E2-17β secretion or maintain it at a higher level than other treatments. 相似文献
16.
Jay F. Kirkpatrick 《Prostaglandins & other lipid mediators》1974,5(1):107-113
Preimplantation mouse embryos were cultured in vitro in concentrations of PGF2α ranging from 5 nanograms/ml to 100 micrograms/ml. Embryos were cultured at the 2-cell stage, 4-cell stage, 8-cell stage and the morula stage and observed for normal development to the blastocyst stage. There was no significant difference (P < .1) between the number of blastocysts attained in the control group and those in the experimental groups. After reaching the blastocyst stage, the embryos were transferred to the uteri of pseudopregnant recipient females. Again, there was no significant difference (P < .3) between controls and PGF2α treated embryos in the number developing to term. These data suggest that exposure to PGF2α does not result in teratogenic effects or early death in preimplantation embryos. 相似文献
17.
The contents of prostaglandins in seminal plasma from a total of 73 men were evaluated. The subjects were grouped as follows: normospermic men, patients with impaired motility, patients with small untreated varicocelle and patients with impaired motility and Kallikrein therapy. Sperm density, morphology and motility were examined. High performance reversed phase liquid chromatography (HPLC) in combination with specific radioimmunoassays were used for the determination of PGE2, PGI2 and PGF2α. There was a significant difference (p < 0, 025; F-test) between the PGI2 concentrations in patients with impaired motility (5,6 ± 1,4 pg/mg protein) and normal men (8,8 ± 3,7 pg/mg protein). PGE2 and PGF2α were significantly different in patients with varicocele (p < 0,025, F-test). Wide ranges of prostaglandins occured in the Kallikrein-group with no significant differences. We conclude that: a) PGI1 is an additional prostaglandin compound in seminal plasma. b)its measurement may not be useful as diagnostic parameter in subfertile men and c) Kallikrein has no influence on the prostaglandin content in seminal plasma and other seminal parameters as motility, motility index and sperm counts. 相似文献
18.
Shiro Ohki Katsuhiro Imaki Fumio Hirata Toshio Hanyu Nobuhiko Nakazawa 《Prostaglandins & other lipid mediators》1974,6(2)
Radioimmunoassays for measuring prostaglandin F2α (PGF2α) and 5α, 7α-dihydroxy-11-keto tetranorprosta-1,16-dioic acid, PGF2α-main urinary metabolite (PGF2α-MUM), with 125I-tyrosine methylester amide (TMA) of PGF2α and PGF2α-MUM were developed.Antibody to PGF2α was produced in rabbits immunized with conjugates of PGF2α coupled to bovine serum albumine. Antibody to PGF2α-MUM was also produced in rabbits immunized with conjugates of PGF2α-MUM coupled to bovine serum albumin.PGF2α-125I-TMA had an affinity to antiserum to PGF2α. PGF2α-MUM-125I-TMA also responded to antiserum to PGF2α-MUM. 相似文献
19.
This study was conducted in vitro to examine factors that may regulate prostaglandin release by bovine trophoblast and endometrial slices. Trophoblastic tissues and endometrial slices were recovered from superovulating and normally-ovulating cattle on day 16 or 20 of pregnancy and incubated for 24 h. Release of PGF2α and 13,14-dihydro-15-keto-PGF2α (PGMF), and incorporation of [14C]-leucine into proteins were quantified and expressed per μg DNA, which gives a measure of cellular activity. Activity of trophoblastic tissue for synthesizing protein was decreased (P<.05) and for releasing PGMF was increased (P<.05) on day 20 compared to day 16 of pregnancy. Neither supercovulation nor day of pregnancy altered trophoblastic activity for releasing PGF2α. Supercovulation increased (P<.05) endometrial release of PGF2α. Endometrial release of PGF2α was less (P<.05) on day 20 than on day 16 of pregnancy. When arachidonic acid (0, 100, 200 or 400 μg) was added at the start of incubation, trophoblastic release of PGF2α changed (P<.05) quadratically with dose of arachidonic acid. When arachidonic acid was added 8 h after the start of incubation, triphoblastic release of PGF2α increased linearly (P<.01) with dose of arachidonic acid. Adding arachidonic acid to incubation medium did not affect trophoblastic or endometrial protein synthesis. Endometrial slices suppressed (P<.05) trophoblastic protein synthesis and release of PGF2α. Apparently, endometrium can modulate trophoblastic release of prostaglandins and synthesis of proteins in vitro, and trophoblastic tissue from supercovulated cattle 16 or 20 days pregnant can be used to study trophoblastic synthesis of prostaglandins and proteins. 相似文献
20.
M. Duchens H. Kindahl M. Forsberg H. Gustafsson H. Rodríguez-Martínet 《Animal reproduction science》1995,40(4):261-268
A study was conducted to determine the effect of suprabasal plasma concentrations of progesterone on the release of prostaglandin F2α (PGF2α) at luteolysis and oestrus. Heifers received silicone implants containing 2.5 (n = 4), 5 (n = 4), 6 (n = 3), 7.5 (n = 3), 10 (n = 4), or 15 (n = 3) g of progesterone, or an empty implant (controls, n = 4) between Days 8 and 25 post ovulation. Blood was collected frequently between Days 14 and 28 and assayed for progesterone and 15-ketodihydroprostaglandin F2α. Basal progesterone concentrations in control heifers did not differ from those in heifers with 2.5- or 5-g implants and remained around 0.4−0.5 nmol l−1 until ovulation in all three groups. In the heifers treated with 6–15 g of progesterone, basal concentrations were maintained at higher (P < 0.05) levels compared with those in the controls, ranging from 0.8 to 1.6 nmol 1−1. The effect of these elevated progesterone levels was to delay ovulation by prolonging the growth of the ovulatory follicle, which continued growing until the implant was removed. In all experimental groups, the first significant increase of the PGF2α metabolite occurred between Days 15.3 and 16.3 (P > 0.05) and was associated with the onset of a decrease in progesterone concentrations, which had reached levels below 3 nmol 1−1 by Days 17.4−19.1. PGF2α metabolite peaks associated with luteolysis were frequent until Day 20. In the period from Day 20 until implant removal, sporadic peaks were observed, ranging in number from 1.0 ± 1.2 (mean ± SEM) in the control group to 3.0 ± 1.4 peaks in the heifers treated with 7.5 g of progesterone (P > 0.05). The number of PGF2α metabolite peaks during that period was higher (P < 0.05) in heifers treated with 10 and 15 g than in controls. A positive correlation was found between the basal concentration of progesterone and the number of PGF2α peaks after luteolysis (r = 0.54; P < 0.01). Plasma progesterone concentrations above approximately 1.4 nmol l−1 were able to maintain the release of PGF2α until the progesterone implants were removed and plasma levels decreased to basal values. These heifers had a preovulatory PGF2α release pattern resembling that found in repeat breeder heifers. 相似文献