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1.
Two experiments were conducted to examine the temporal aspects of luteal resistance to the luteolytic effect of prostaglandin (PG) F2 alpha during early pregnancy. In Exp. 1, 14 pregnant and 12 nonpregnant ewes were treated with PGF2 alpha either on d 10 or 13 post-estrus. Jugular venous blood samples were collected at -30 min, 0, 6, 12, 18, 24, 30 and 36 h post-injection for quantification of progesterone. The difference (delta P) between pre-treatment and post-treatment concentrations of progesterone was calculated for each ewe. There was a significant interaction between pregnancy status and day of treatment on delta P (P less than .05). Pregnant and nonpregnant ewes treated on d 10 showed a large delta P. A large delta P also was observed in nonpregnant ewes treated on d 13 post-estrus. However, delta P in pregnant ewes treated on d 13 was smaller than in the other three groups (P less than .05). The temporal patterns of concentrations of progesterone in serum were different among treatment groups (P less than .05). A suppression in the concentration of progesterone was observed by 24 h post-injection in all four treatment groups. Progesterone returned to pre-treatment levels only in pregnant ewes treated on d 13. In Exp. 2, 47 pregnant ewes were treated with PGF2 alpha on d 10, 13, 16, 19, 22, 26 or 30 postestrus. Blood samples were collected and data were analyzed as described for Exp. 1.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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3.
The hypothesis that subnormal luteal function after induced ovulation in anestrous ewes was the result of uterine influences exerted during the periovulatory period was tested. Crossbred ewes (n = 27) in seasonal anestrus were induced to ovulate by administration of 12 doses of 250 ng of LHRH at 2-h intervals, followed immediately by a bolus injection of LHRH (250 micrograms; d 0). Ewes were unilaterally hysterectomized on either d -3 (PRELHRH) or 2 (POSTLHRH). Daily blood samples were collected and assayed for progesterone (P4) and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM). All ewes were slaughtered on d 10, and corpora lutea (CL) were collected, weighed, and assayed for concentration of P4. All ewes that ovulated exclusively in the ovary ipsilateral to the remaining uterine horn had a transient increase in plasma P4 of 2 to 3 d (short luteal phase). In ewes with at least one CL in the isolated ovary, elevated plasma P4 was maintained after hysterectomy but was consistently lower (P less than .05) in POSTLHRH ewes than in PRELHRH ewes. Concentrations of PGFM did not differ between treatments. The CL ipsilateral to the remaining uterine horn weighted less (P less than .01) and contained less P4 (P less than .01) than contralateral CL. These data confirm the hypothesis that premature regression of subnormal CL is uterine-dependent in a local fashion. Presence of the uterus during the follicular and(or) early luteal phase inhibited subsequent luteal function in seasonally anestrous ewes. 相似文献
4.
The objective of the present study was to determine the temporal relationships among luteal adenylate cyclase activity, luteal phosphodiesterase activity, luteal progesterone concentration and plasma progesterone concentration during prostaglandin F2 alpha (PGF2 alpha)-induced luteolysis in ewes. Corpora lutea (CL) were removed from cycling ewes on d 9 (d 0 = first day of estrus) at 0, 2, 4, 6, 12 and 24 h (seven to eight ewes/group) after PGF2 alpha administration (im). Jugular blood samples were collected at the time of enucleation of CL and analyzed for progesterone. Plasma and luteal progesterone concentrations were decreased (P less than .05) by 4 and 12 h after PGF2 alpha injection, respectively. Basal adenylate cyclase, luteinizing hormone (LH)-activated adenylate cyclase, guanylylimidodiphosphate [Gpp(NH)p]-activated adenylate cyclase and LH plus Gpp(NH)p-activated adenylate cyclase activities were decreased (P less than .05) by 2 h after PGF2 alpha injection. The decrease in adenylate cyclase activity paralleled the decrease in plasma progesterone concentration over time. Luteinizing hormone stimulated (P less than .05) adenylate cyclase activity relative to basal activity at 0, 2, 12 and 24 h post-PGF2 alpha; whereas, Gpp(NH)p stimulated (P less than .01) adenylate cyclase activity relative to basal activity at each time point. In contrast to the decrease in adenylate cyclase activity, phosphodiesterase activity was increased (P less than .05) at 2 and 4 h post-PGF2 alpha. These results suggest that a decrease in adenylate cyclase activity coupled with an increase in phosphodiesterase activity may decrease the intracellular adenosine 3',5' cyclic monophosphate (cAMP) concentration.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
In three experiments, we examined the effects of suckling, progestogen treatment, hysterectomy or exogenous gonadotropin releasing hormone (GnRH) on ovarian function in autumn-lambing, postpartum ewes. In each experiment, GnRH was injected on approximately d 25 postpartum. Suckling reduced (P less than .01) GnRH-induced release of luteinizing hormone (LH) but not of follicle stimulating hormone (FSH), and reduced (P less than .05) the proportion of ewes that developed corpora lutea in response to GnRH. Suckling had no effect on duration (8.8 d) of GnRH-induced luteal phases. Progestogen prior to GnRH increased (P less than .01) the duration of the first luteal phase (10.1 vs 7.6 d; progestogen-treated ewes vs control ewes), but progestogen did not affect the release of LH or FSH. Progestogen treatment did not alter the interval from parturition to the first detected estrus (42.6 d). The concentration of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) just after lambing was greater than 400 pg/ml of jugular plasma, but concentrations of PGFM declined thereafter. Hysterectomy the day after lambing hastened (P less than .001) the decline in concentrations of PGFM, indicating that prostaglandins from the postpartum uterus probably caused the high concentrations of PGFM in jugular plasma. Hysterectomy reduced (P less than .05) the interval from parturition to detectable luteal function (19.6 vs 25.3 d) and enhanced (P less than .001) luteal production of progesterone. This study of autumn-lambing ewes indicates that the uterus has a negative effect on ovarian function and that suckling and progestogen affect ovarian response to GnRH. 相似文献
6.
J P Copelin M F Smith H A Garverick R S Youngquist W R McVey E K Inskeep 《Journal of animal science》1988,66(5):1236-1245
The objective of this study was to determine if corpora lutea anticipated to have short lifespans were more responsive to the luteolytic action of prostaglandin F2 alpha (PGF2 alpha) than corpora lutea anticipated to have normal lifespans. Sixteen cows were allotted randomly to a hysterectomized-control (HC) or hysterectomized-progestogen (norgestomet) implant (HN) group. To verify that progestogen treatment of postpartum cows prior to induction of ovulation with gonadotropin-releasing hormone (GnRH) results in an increased number of cows exhibiting normal-length luteal phases, 21 additional cows were allotted randomly to a uterine intact-control (IC) or a uterine intact-progestogen implant (IN) group. Cows allotted to the HN and IN groups received norgestomet ear implants for 9 d beginning 17 to 21 d postcalving. All cows were injected (i.m.) with 100 micrograms GnRH 28 to 32 d postcalving (48 h after implant removal in the HN and IN groups) to induce ovulation. Two or 3 d after GnRH injection (d 0), cows in the HC (n = 8) and HN (n = 8) groups were hysterectomized to remove the major endogenous source of PGF2 alpha, and on d 7 cows were injected (i.m.) with 10 mg PGF2 alpha to assess luteal sensitivity. The proportion of corpora lutea having normal lifespans was greater (P less than .1) for the IN than for the IC group. In HC and HN groups, concentration of progesterone (P) increased similarly from d 0 to 6. Injection of PGF2 alpha in HC and HN groups on d 7 decreased (P less than .01) concentration of P approximately 50% by 6 h after injection (similar for both groups). Complete luteolysis was induced by PGF2 alpha in none of eight and two of eight cows in the HC and HN groups, respectively. In remaining cows (HC and HN groups) concentration of P increased (P less than .01; similar for HC and HN groups) beginning 24 h after PGF2 alpha and remained elevated through d 30 to 34 (end of experimental-period). In summary, corpora lutea anticipated to be short-lived were not more responsive to PGF2 alpha than corpora lutea anticipated to have normal lifespans. 相似文献
7.
Percentages of normal and apoptotic parenchymal cells, fibroblasts and endothelial cells in ovine corpora lutea at 12, 24 and 36 hr following administration of a luteolytic dose of PGF2 alpha were determined and compared to percentages for identical cell types in corpora lutea removed from control ewes on days 10 (n = 5) and 12 (n = 6) postestrus. In corpora lutea obtained from control ewes greater than or equal to 95% of nuclei examined were scored normal for each of the respective cell types with no difference (P greater than .05) observed between luteal tissue obtained on days 10 and 12 postestrus. Following treatment with PGF2 alpha there were significant (P less than .05) reductions in the percentages of nuclei scored normal. Compared to controls the percentage of endothelial cell nuclei scored normal was reduced at 12 hr following PGF2 alpha-treatment; however significant reductions in percentages of parenchymal and fibroblast nuclei scored normal were not evident until 24 and 36 hr, respectively. Consistent with the concept of apoptosis, nuclear condensation and/or margination indicative of apoptosis did not occur synchronously within a given cell type: i.e., irrespective of the time point examined some cells appeared normal, whereas others had undergone nuclear condensation and/or margination. A sequence of events to explain structural and functional changes that occur during luteolysis following the interaction of PGF2 alpha with specific receptors in large steroidogenic luteal cells is discussed. 相似文献
8.
The effect of pretreatment with flurogestone acetate (FA) on the lifespan of corpora lutea induced with pregnant mare serum gonadotropin (PMS) was examined in cycling and anestrous ewes. Cycling ewes received one of three treatments: 750 IU PMS 2 d before expected estrus (P), FA-impregnated vaginal sponges for 16 d (F), and FA sponges for 16 d and 750 IU PMS 2 d before sponge removal (FP). A fourth group served as controls (C). When compared with d 12 means within treatment, plasma progesterone means were lower (P less than .05) on d 16 in control ewes, on d 15 in P and F ewes, and on d 14 in FP ewes. Only 44% of ewes receiving FA treatment alone exhibited estrus (P less than .05) compared with 100% of untreated ewes. The FP treatment increased ovulation rate compared with controls (P less than .01). The decrease in luteal lifespan observed in cycling ewes suggests a possibility of asynchrony between the uterus and embryo, which could result in failure of an embryo to prevent luteal regression, thus resulting in reduced fertility. None of the seasonally anestrous ewes that received PMS alone and only 55% of those treated with FA sponges for 8 d before PMS injection exhibited estrus. Ewes pretreated with FA exhibited higher plasma progesterone concentrations on d 10 through 16 after PMS injection. There were no differences in luteal lifespan as measured by peripheral plasma progesterone patterns. Although FA treatment did not alter luteal lifespan in anestrous ewes, the increased plasma progesterone concentrations observed with FA treatment suggest that progestogen pretreatment may be essential for optimal luteal function. 相似文献
9.
Experiments were undertaken to determine whether the conceptus renders a corpus luteum resistant to the luteolytic action of prostaglandin F2 alpha (PGF2 alpha), and modulates release of this prostaglandin by the uterus of early pregnant ewes. Prostaglandin F2 alpha was luteolytic when administered to indomethacin-treated ewes on d 10 and 11 of the estrous cycle. The same PGF2 alpha treatment was not luteolytic when applied on d 19 and 20 of pregnancy in ewes treated with indomethacin. Pulsatile release of PGF2 alpha (measured by 15-keto-13,14-dihydro PGF2 alpha-PGF2 alpha plasma level, PGFM) was observed between d 14 and 16 of the cycle but not during the same period of pregnancy. Ablation of the conceptus on d 17 resulted in progressive restoration of PGFM surges and subsequent luteolysis. Estradiol-17 beta (E2-17 beta) administration on d 12 of the cycle induced earlier PGFM surges and luteal regression. The same E2-17 beta treatment administered on d 14, 19 and 33 of pregnancy failed to induced PGFM pulses and luteolysis. In the absence of the conceptus (surgical ablation), E2-17 beta treatment was luteolytic (PGFM surges) on d 17 but not on d 33. We conclude that the conceptus controls the amount and pattern of PGF2 alpha released by the uterus, as well as the sensitivity of the uterus to E2-17 beta as early as d 14 of pregnancy. Simultaneously, an embryonic protective effect takes place at the luteal level. 相似文献
10.
N S Braun E Heath J R Chenault R D Shanks J E Hixon 《American journal of veterinary research》1988,49(4):516-519
Corpora lutea were collected from 18 beef heifers on day 4 or 12 of the estrous cycle, 1 hour after prostaglandin (PG) F2 alpha or saline (control) treatment. Five heifers also were treated with PGF2 alpha on day 4, but their corpora lutea were not collected until day 12. The relative percentage of cytoplasm occupied by granules decreased only in large luteal cells (LLC) in heifers given PGF2 alpha on day 12, compared with the percentage in controls. Small luteal cells (SLC) were not as affected. The luteal concentration of progesterone was similarly decreased only in heifers given PGF2 alpha on day 12. Treatment of heifers with PGF2 alpha on day 4 had no marked effect on progesterone values or on the relative percentage of cytoplasm occupied by granules in LLC or SLC. Seemingly, LLC were more responsive to PGF2 alpha than were SLC, and PGF2 alpha treatment of beef heifers at day 4 did not markedly impair luteal function. 相似文献
11.
Fourteen anovulatory postpartum (38.0 +/- 1.9 d) beef cows that ovulated after an injection of 250 micrograms gonadotropin releasing hormone (GnRH) in saline were used to examine the influence of indomethacin on luteal function. Beginning the d after GnRH, 6 cows were given intrauterine infusions of indomethacin for 14 d and the other eight cows received vehicle. After GnRH treatment, concentrations of progesterone in serum were elevated longer (P less than .01) for indometacin-treated cows than for vehicle-treated cows. At the same time prostaglandin metabolite (PGFM) concentrations were lower (P less than .01) in indomethacin-treated cows than in vehicle-treated cows. In summary, indomethacin suppressed PGFM concentrations and enhanced function of corpora lutea induced in postpartum suckled beef cows. 相似文献
12.
F. Gamboni T.A. Fitz P.B. Hoyer M.E. Wise M.H. Mayan G.D. Niswender 《Domestic animal endocrinology》1984,1(1):79-88
Experiments were conducted to determine the effect of additional gonadotropic support on induced corpora lutea of anestrous ewes. In one series of experiments, ewes were superovulated and half the ewes received an i.v. injection of 500 IU human chorionic gonadotropin (hCG) on day 5 after ovulation. Corpora lutea were collected from both groups on day 10 after ovulation. Dissociated corpora lutea collected from ewes which received additional hCG contained proportionately more large luteal cells than did those from control ewes (P<.05). In neither cell type was content of receptors for luteinizing hormone (LH) or secretion of progesterone in response to LH affected by an additional injection of hCG. Large cells from anestrous ewes produced more progesterone in response to LH (P<.05) than did large cells from similarly treated ewes during the breeding season. Small cells collected during either season responded similarly to LH. In another series of experiments, anestrous ewes were induced to ovulate and were exposed to fertile rams. Half the ewes received an i.v. injection of 500 IU hCG on day 5 after ovulation. Serum content of progesterone was higher on day 10 in ewes which received hCG 5 days earlier than in control ewes, although progesterone levels declined to generally nondetectable levels in nonpregnant ewes of both groups by day 16. Pregnancy rates in the two groups were not different. We concluded that additional gonadotropic support affects the morphology and function of corpora lutea from anestrous ewes and may be useful for enhancing fertility during the nonbreeding season. 相似文献
13.
The objective of the current study was to evaluate the effect of omega-3 fatty acids in fish meal on mitigating uterine PGF2alpha synthesis in heifers with low luteal-phase concentrations of progesterone. Animals were individually fed a corn silage-based diet supplemented with fish meal (5% of DMI; n = 12) or corn gluten meal (6% of DMI; n = 13). Estrous cycles were synchronized using PGF2alpha beginning on d 25 of supplementation. Random heifers from each supplement group (n = 6 fish meal, and n = 7 corn gluten meal) were given three additional i.m. injections of PGF2alpha (25 mg) at 12-h intervals beginning at 0600 on d 3 after estrus to induce formation of corpora lutea that secrete lower concentrations of progesterone. Jugular blood samples were collected daily commencing on d 1 and continuing through d 16 of the estrous cycle to determine serum progesterone concentrations. Oxytocin was administered i.v. (100 IU) to heifers on d 16 after estrus to stimulate uterine PGF2alpha synthesis. Before statistical analyses, heifers were sorted to either normal or low luteal-phase progesterone as determined from serum progesterone on d 9 of the estrous cycle. After sorting, treatment groups consisted of 1) normal luteal progesterone + fish meal (n = 6); 2) low luteal progesterone + fish meal (n = 6); 3) normal luteal progesterone + corn gluten meal (n = 6); and 4) low luteal progesterone + corn gluten meal (n = 7). Serum concentrations of the PGF2alpha metabolite following oxytocin stimulation tended (P = 0.09) to be greater in heifers with low luteal-phase progesterone compared with heifers with normal luteal-phase progesterone. Fish meal supplementation mitigated this response in heifers with low luteal-phase progesterone (P < 0.05), but had no effect on heifers with normal luteal-phase progesterone. In conclusion, the omega-3 fatty acids in fish meal seem to decrease uterine PGF2alpha synthesis in heifers with low luteal-phase serum concentrations of progesterone. 相似文献
14.
A Nakajima S Hiraizumi K Onodera H Suzuki Y Kudo I Domeki 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(1):95-98
Thirteen beef cows were superovulated using 4,000 i.u. of pregnant mare serum gonadotrophin (PMSG) on days 9 to 14 of the estrous cycle, followed by two injections of 500 micrograms prostaglandin F2 alpha analogue (PGF2 alpha) 48 and 55 hrs later. Seven of them were injected intramuscularly with bovine anti-PMSG serum 12 hrs after the first signs of estrus. The remaining 6 cows were served as controls and received no antiserum. Peripheral blood concentrations of progesterone (P) and estradiol-17 beta (E2) were compared in relation to the superovulatory responses. The injection of anti-PMSG serum did not significantly affect the numbers of the corpora lutea (CL), the anovulatory follicles and the transferable embryos at 7 to 8 days after superovulatory estrus, but increased the ratio of embryos classified as excellent or good quality. Although the plasma P concentration showed no significant differences between the anti-PMSG-treated and control cows, the plasma E2 concentration displayed a characteristic difference, suppressing the second E2 peak in the anti-PMSG-treated cows. It is concluded that the use of bovine anti-PMSG serum for PMSG/PGF2 alpha-treated cows at 12 hrs after the beginning of the estrus improves the quality of embryos recovered, probably due to inhibition of high estrogenic environment following ovulation. 相似文献
15.
Son DS Choe CY Cho SR Choi SH Kim HJ Hur TY Jung YG Kang HG Kim IH 《The Journal of reproduction and development》2007,53(6):1313-1318
This study evaluated the pregnancy rates following either a controlled internal drug release (CIDR)-based timed artificial insemination (TAI) or an embryo transfer (TET) protocol compared with that following a single PGF(2alpha) injection and AI after estrus (AIE) in lactating repeat breeder dairy cows. Fifty-three lactating dairy cows diagnosed as repeat breeders were used in this study and were randomly assigned to the following three treatments. (1) Cows, at random stages of the estrous cycle, received a CIDR device and 2 mg estradiol benzoate (EB; Day 0), a 25 mg PGF(2) (alpha) injection at the time of CIDR removal on Day 7 and a 1 mg EB injection on Day 8. The cows then received TAI 30 h (Day 9) after the second EB injection using dairy semen (TAI group, n=13). (2) Cows, at random stages of the estrous cycle, received the same hormonal treatments as in the TAI group. The cows then received TET on Day 16 using frozen-thawed blastocysts or morula embryos collected from Korean native cattle donors (TET group, n=13). (3) Cows, at the luteal phase, received a 25 mg injection of PGF(2alpha) and AIE using dairy semen (control group, n=27). The ovaries of the cows in the TET group were examined by transrectal ultrasonography to determine ovulation of the preovulatory follicles, and blood samples were collected for serum progesterone (P4) analysis. The pregnancy rate was significantly higher in the TET group (53.8%) than in the control (18.5%) or TAI (7.7%) groups (P<0.05). The ultrasonographic observations demonstrated that all the cows in the TET group ovulated the preovulatory follicles and concomitantly formed new corpora lutea. Accordingly, the mean serum P4 concentration remained constant between Day 0 and Day 7 of the luteal phase, decreased dramatically on Day 8 (P<0.01) and subsequently increased by Day 16 (P<0.01). These data suggest that the CIDR-based TET protocol can be used to effectively increase the pregnancy rate in lactating repeat breeder dairy cows. 相似文献
16.
CA Letelier MA Sanchez RA Garcia‐Fernandez B Sanchez P Garcia‐Palencia A Gonzalez‐Bulnes JM Flores 《Reproduction in domestic animals》2011,46(3):481-488
The aim of the current study was to determine the possible effects of progestagen oestrous synchronization on vascular endothelial growth factor (VEGF) expression during sheep luteogenesis and the peri‐implantation period and the relationship with luteal function. At days 9, 11, 13, 15, 17 and 21 of pregnancy, the ovaries from 30 progestagen treated and 30 ewes cycling after cloprostenol injection were evaluated by ultrasonography and, thereafter, collected and processed for immunohistochemical evaluation of VEGF; blood samples were drawn for evaluating plasma progesterone. The progestagen‐treated group showed smaller corpora lutea than cloprostenol‐treated and lower progesterone secretion. The expression of VEGF in the luteal cells increased with time in the cloprostenol group, but not in the progestagen‐treated group, which even showed a decrease between days 11 and 13. In progestagen‐treated sheep, VEGF expression in granulosa‐derived parenchymal lobule capillaries was correlated with the size of the luteal tissue, larger corpora lutea had higher expression, and tended to have a higher progesterone secretion. In conclusion, the current study indicates the existence of deleterious effects from exogenous progestagen treatments on progesterone secretion from induced corpora lutea, which correlate with alterations in the expression of VEGF in the luteal tissue and, this, presumably in the processes of neoangiogenesis and luteogenesis. 相似文献
17.
Miyamoto A Shirasuna K Wijayagunawardane MP Watanabe S Hayashi M Yamamoto D Matsui M Acosta TJ 《Domestic animal endocrinology》2005,29(2):329-339
Prostaglandin F2alpha (PGF2alpha) is the primary luteolysin in the cow. During the early luteal phase, the corpus luteum (CL) is resistant to the luteolytic effect of PGF2alpha. Once mature, the CL becomes responsive to PGF2alpha and undergoes luteal regression. These actions of PGF2alpha coincide with changes in luteal blood flow (BF): PGF2alpha has no effect on BF in the early CL, but acutely increases BF in the peripheral vasculature of the mature CL within 30 min of PGF2alpha injection. During spontaneous luteolysis, luteal BF increases on Days 17-18 of the estrous cycle, prior to any decrease in plasma progesterone (P). The increase in luteal BF is synchronous with an increase in plasma PGFM levels, suggesting that pulsatile release of PGF2alpha from uterus stimulates the increase in luteal BF. Serial biopsies of these CL showed that mRNA expression for endothelial nitric oxide synthase (eNOS) together with endothelin-1 (ET-1) and angiotensin converting enzyme (ACE) increases on Days 17-18 when the luteal BF is elevated. On Day 19 when plasma P level firstly decreases, eNOS mRNA returns to the basal level whereas ET-1 and ACE mRNA remains elevated. Cyclooxygenase-2 (COX-2) mRNA expression increases on Day 19. In support of these data, an in vivo microdialysis study revealed that luteal ET-1 and angiotensin II (Ang II) secretion increases and precedes PGF2alpha secretion during spontaneous luteolysis. In conclusion, we show for the first time that an acute increase of BF occurs in the peripheral vasculature of the mature CL together with increases in eNOS expression and ET-1 and Ang II secretion in the CL during the early stages of luteolysis in the cow. We propose that the increase in luteal BF may be induced by NO from large arterioles surrounding the CL, and simultaneously uterine or exogenous PGF2alpha directly increases ET-1 and Ang II secretion from endothelial cells of microcapillary vessels within the CL, thereby suppressing P secretion by luteal cells. Taken together, our results indicate that an acute increase in luteal BF occurs as a first step of luteolysis in response to PGF2alpha. Therefore, local BF plays a key role to initiate luteal regression in the cow. 相似文献
18.
A study was done to test whether ovulatory follicles destined to form subfunctional corpora lutea differed from normal ovulatory follicles in steroidogenic function. Twenty-five ewes were treated with prostaglandin F2 alpha on d 11 of the estrous cycle, then unilaterally ovariectomized before (n = 13) or after (n = 12) the surge of luteinizing hormone (LH) at the induced estrus to collect "control" follicles, which would have produced normal corpora lutea. In 15 ewes, the second ovary was removed 63 to 84 h later to collect "treated" follicles before (n = 7) or after (n = 8) the second expected surge of LH. Five ewes (control) were allowed to ovulate from the remaining ovary at first estrus and another five (treated) at the second estrus (3 to 4 d later). Treated ewes had lower serum progesterone than control ewes during the ensuing cycle (P less than .05). Treated follicles contained less estradiol in the theca (4.4 +/- .6 vs 10.0 +/- 2.5 ng; P less than .05), less androstenedione (.1 +/- .1 vs 1.0 +/- .2 ng) and estradiol (.5 +/- .1 vs 2.9 +/- 2.2 ng) in the granulosa (P less than .05) and less progesterone in the follicular fluid (.8 +/- .4 vs 3.3 +/- .8 ng; P less than .05) than control follicles, when removed before the surge of LH. Follicles removed after the surge of LH did not differ. In conclusion, ovulatory follicles with low steroidogenic function became corpora lutea that secreted lower-than-normal quantities of progesterone. 相似文献
19.
Cushman RA Davis PE Boonyaprakob U Hedgpeth VS Burns PJ Britt JH 《Journal of animal science》1999,77(11):2883-2885
We determined whether a single injection of slow-release estradiol-17beta (SRE2) would induce pseudopregnancy in gilts and whether PGF2alpha would regress the corpora lutea (CL) of pseudopregnancy. Crossbred gilts (n = 40) were induced to ovulate by treatment with 400 IU of hCG + 200 IU of eCG (PG600, Intervet, Millsboro, DE) given at 180 d of age (d = 0). On d 14, gilts were injected i.m. with one of five doses (n = 8 gilts/dose) of SRE2 (0, 12.5, 25, 50, or 100 mg). Blood samples were collected before SRE2 and twice weekly until d 73 to monitor serum progesterone (P4) and estradiol (E2). On d 59, gilts received (i.m.) 10 mg of PGF2alpha (Lutalyse, Pharmacia Upjohn, Kalamazoo, MI) and were checked for estrus for 7 d. On d 62, mammary development was scored (0 = no development; 1 = some development; 2 = teat and gland development) by a neutral observer. Treatment with SRE2 increased (P < .05) peak E2 concentrations, duration of luteal function, and mammary gland score. There were no differences (chi-square, P > .05) among doses of SRE2 in the percentage of pseudopregnant gilts that showed luteolysis after PGF2alpha. We conclude that a single injection of SRE2 can induce pseudopregnancy and that the CL can be regressed with PGF2alpha, providing a simple method for controlling estrus in gilts. 相似文献
20.
The ability of ovine placental lactogen (oPL) to stimulate progesterone secretion of porcine luteal cells isolated from ovaries in different stages of the oestrous cycle and to support the luteotropic action of PGE2 or to protect the corpus luteum (CL) against the luteolytic action of PGF2 alpha was investigated. oPL in all doses used had no effect on progesterone production of cells isolated from early developing corpora lutea while in doses of 1 and 10 ng/ml it increased oestradiol secretion by this type of cells. In doses of 1, 10 and 100 ng/ml it also increased progesterone secretion of cells isolated from mature corpora lutea in a dose-dependent manner. No influence on progesterone production of cells isolated from regressing corpora lutea was observed. oPL added to the culture media had no effect on PGE2-stimulated progesterone production by cells isolated from mature corpora lutea. However, it exerted a protective effect against the luteolytic action of PGF2 alpha observed in cultures treated with PGF2 alpha alone or in combination with PGE2 in a ratio of 4:1. These studies provide evidence that oPL is luteotropic and supports progesterone production in swine. The fact that oPL acted directly on ovarian steroidogenesis suggests that it may also play some role under non-pregnant physiological conditions. Future studies of structural and functional proteins secreted by the porcine conceptus will help resolve this uncertainty. 相似文献