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PubMed1992

Paracrine actions of oxytocin, prostaglandin F2 alpha, and estradiol within the human corpus luteum.

Human luteal cells are known to interact in an auto- and paracrine fashion using a variety of substances, including prostaglandins (PGs), steroids, and peptides. In cultures of dispersed luteal cells obtained from several animal species prostaglandin F2 alpha (PGF2 alpha) and oxytocin (OXT) inhibit progesterone (P) secretion, indicating a luteolytic effect of these substances. The disadvantage of luteal cell cultures is that the different luteal cell types do not communicate with each other, i.e. auto- and paracrine effects cannot be studied. Therefore, we used a microdialysis tubing, which is implanted in human corpora lutea (CL) kept under short term organ culture conditions. Ringer's solution is pumped through the dialysis tubing, and substances secreted by the luteal tissue can be determined in the effluent fractions. This system also allows topical application of substances with putative intraluteal effects. In the present report we used PGF2 alpha, OXT, and estradiol (E2) to examine the effects of these substances on the respective other hormones and on P release from young human CL. Intraluteal application of PGF2 alpha stimulated OXT, E2, and P release. OXT was stimulatory to E2 and P secretion, an effect that can be blocked by a specific OXT antagonist and by tamoxifen. Elevation of intraluteal E2 concentrations also had marked stimulatory effects on P secretion. From luteal cell culture experiments it is known that PGF2 alpha and OXT have direct inhibitory effects on P production, but both substances stimulate E2 release. It was also shown that E2 counteracts the inhibitory effects on P release. Therefore, the PGF2 alpha- and OXT-induced E2 release may be responsible for the increased P release. This assumption is further substantiated by the observation that intraluteally applied E2 stimulates P secretion, and preexposure of human CL to tamoxifen prevents the OXT-induced stimulation of P, but not E2, secretion. We conclude that in young human CL, PGF2 alpha and OXT have dual effects: direct inhibitory effects on P release and E2-mediated stimulatory effects, which in young CL result in a net stimulation of P secretion.

Chorionic Gonadotropin↗

PubMed1989

Functional and morphological characteristics of the first corpus luteum formed after parturition in ewes.

The ability of sheep luteal cells from the first corpus luteum formed after parturition (Group F) to secrete progesterone in the presence or absence of LH was compared with that of luteal cells obtained from normal cyclic ewes (Group C). Luteal concentrations of receptors for LH and prostaglandins (PG) F-2 alpha (PGF-2 alpha) and the cellular composition of corpora lutea from Groups F and C were also compared. Luteal cells from Group F secreted less progesterone in either the presence or absence of LH (P less than 0.01). There was no difference in the number of receptors for LH or PGF-2 alpha per luteal cell between Groups F and C (P greater than 0.1), nor was there a difference in the number of large or small steroidogenic luteal cells (P greater than 0.1). It was concluded that, if short-lived corpora lutea are insensitive to gonadotrophins, this response is not mediated by decreased numbers of receptors for LH. In addition, if the first corpus luteum formed post partum in ewes is more sensitive to the luteolytic effects of PGF-2 alpha, this effect is not mediated by an increased number of receptors for PGF-2 alpha or an increased proportion of PGF-2 alpha-sensitive large luteal cells.

Animals↗

PubMed1994

Luteal oxytocin and monoestry in the roe deer Capreolus capreolus.

The relationship between the corpus luteum and the uterus in terms of the secretion of oxytocin and PGF2 alpha was investigated in free-living and captive roe deer Capreolus capreolus. During the breeding season the corpus luteum contained oxytocin and oxytocin-neurophysin mRNA, and secreted oxytocin in response to administration of the PGF2 alpha analogue cloprostenol. The oxytocin receptor was present in the uterus during the bleeding season and during delayed implantation; however, in contrast to the situation observed in other ruminants in which it has been studied, administered oxytocin did not stimulate uterine secretion of PGF2 alpha. Trophoblast interferon was undetectable at any stage of conceptus development. The absence of the mechanism underlying episodic uterine secretion of PGF2 alpha during luteolysis, which may account for the monoestry of roe deer, is consistent with the previously observed luteolytic effect of the PGF2 alpha analogue.

Animals↗

PubMed1994

Mechanisms controlling corpus luteum function in the rhesus monkey (Macaca mulatta): inhibitory action of hCG on luteolysis induced by PGF2 alpha.

The aim of this study was to determine whether daily increasing doses of hCG could overcome luteal regression induced by PGF2 alpha in rhesus monkeys. Prostaglandin F2 alpha (10 ng microliters-1 h-1) or vehicle (tham buffer; 1 microliter h-1) was infused directly into the corpus luteum for 7 days, beginning 7 days after the preovulatory oestradiol surge. hCG was injected i.m. in increasing doses (15, 30, 60, 90, 180, 360 and 720 iu) for 7 days, starting on the eighth day after the preovulatory oestradiol surge, or 1 day after the initiation of luteal infusion of PGF2 alpha or vehicle. Monkeys receiving vehicle plus hCG on the same days served as controls. Daily progesterone, oestradiol and hCG concentrations were determined from blood drawn from the saphenous or femoral vein, and the duration of the luteal phases were recorded. Where intraluteally infused PGF2 alpha resulted in premature, functional luteolysis, hCG always inhibited the luteolytic effect of PGF2 alpha; the secretory patterns of progesterone and oestradiol were augmented, and peak values were reached in concert with the highest concentration of hCG in the blood, and the luteal phase was significantly increased compared with those of untreated monkeys or with monkeys treated with PGF2 alpha alone or vehicle. Treatment with hCG alone or with PGF2 alpha vehicle also resulted in maintained luteal function and a significantly longer luteal phase, but both progesterone and oestradiol concentrations began to decline before hCG reached peak values in the circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Luteolytic potency of a prostaglandin analogue at different stages of the oestrous cycle in red deer (Cervus elaphus) hinds.

The luteolytic effect of the prostaglandin F2 alpha analogue, cloprostenol, was investigated in red deer by monitoring concentrations of plasma progesterone, the induction of oestrus and ovulation, and fertility. Oestrus was synchronized in 48 adult hinds by intravaginal delivery of exogenous progesterone for 12 days and i.m. injection of 250 iu pregnant mares' serum gonadotrophin at progesterone withdrawal. A single i.m. dose of 500 micrograms cloprostenol was administered at day 4, 6, 8, 10, 12, 14 or 16 of the subsequent oestrous cycle (n = 6 hinds per treatment; day 0 = oestrus). Six other hinds were monitored by intensive collection of blood samples between day 16 and day 19 to define changes in plasma progesterone concentrations during spontaneous luteolysis. Samples of jugular blood, collected every second day throughout the study and every 6 h for 78 h from the time of administration of cloprostenol, were analysed for plasma concentrations of progesterone and LH. Oestrus was detected by continuous observation during the period of intensive collection of blood samples and all hinds were subjected to transrectal ultrasonography to assess pregnancy status. On the basis of changes in plasma progesterone concentrations, cloprostenol induced complete luteolysis in all hinds treated on days 8-16 and in five of six hinds treated on day 6. Oestrus, ovulation and conception occurred in 25 (69%), 28 (78%) and 25 (69%), respectively, of hinds treated on days 6-16 inclusive (n = 36). Luteolysis was incomplete in all hinds treated on day 4, and none of the animals exhibited oestrus or ovulated; luteolysis was incomplete for one hind treated on day 6.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1998

Depletion of vitamin C from pig corpora lutea by prostaglandin F2 alpha-induced secretion of the vitamin.

The luteolytic effects of prostaglandin F2 alpha (PGF2 alpha) are thought to be mediated in part by the promotion of an increasingly oxidative cellular environment. Loss of antioxidants is one mechanism by which PGF2 alpha might induce or exacerbate oxidative damage within the corpus luteum. This study was performed to establish whether depletion of vitamin C is an acute effect of PGF2 alpha on the pig corpus luteum and to gain insight into the mechanism of luteal vitamin C loss at luteolysis. Gilts (n = 4) were anaesthetized and both utero-ovarian veins and an ear vein were catheterized. Each corpus luteum on the treated ovary received an intraluteal injection of PGF2 alpha (1 microgram) followed by a sustained release implant containing 100 micrograms of the prostaglandin. The other ovary served as the control and each corpus luteum received corresponding volumes of injection vehicle and blank implant. Blood was collected from the ear vein and both utero-ovarian veins every 15 min beginning 15 min before the onset of treatment. Collection of blood stopped when animals were ovariectomized and corpora lutea were collected at 2 h after treatment. Progesterone and vitamin C (ascorbate) concentrations were measured in tissue and plasma samples. PGF2 alpha-treated luteal tissue had similar progesterone, but significantly lower ascorbate, concentrations when compared with control corpora lutea. PGF2 alpha treatment resulted in a rapid and sustained increase in plasma ascorbate within the treatment-side utero-ovarian vein, while the control utero-ovarian vein and ear vein showed little change in plasma ascorbate during the experimental period. No effect of PGF2 alpha on plasma progesterone was evident. This finding suggests that PGF2 alpha depletes the pig corpus luteum of vitamin C by inducing secretion of the vitamin into the bloodstream. Further studies are necessary to determine whether the depletion of vitamin C that is induced by PGF2 alpha contributes to the demise of the pig corpus luteum.

Analysis of Variance↗

PubMed1997

Roles of reactive oxygen species in the regulation of luteal function.

Ephemerality and prolongation of luteal function have been matters of great concern in reproduction for many years. However, their control mechanisms are very complex and differ among mammals. Recently, evidence has indicated that reactive oxygen species may play important roles in the regulation of luteal function. Reactive oxygen species are present in most somatic cells and are involved in apoptosis, or 'physiological cell death'. In the corpus luteum, reactive oxygen species also exert luteolytic effects as well as some paradoxical luteotrophic effects. This paper discusses the possible roles of reactive oxygen species in the control of luteal function.

Animals↗

PubMed1975

Plasma progesterone levels in guinea-pigs actively immunized against prostaglandin F2alpha, hysterectomized or treated with intra-uterine indomethacin.

Five guinea-pigs actively immunized against a prostaglandin F2alpha(PGF2alpha)-bovine serum albumin conjugate showed elongated oestrous cycles. During these, corpora lutea were maintained in a functional secretory state as indicated by plasma progesterone levels. The results are compatible with the view that the PGF2alpha antibodies neutralized the PGF2alpha released from the uterus and thus prevented its normal luteolytic effect. Similar patterns of progesterone secretion were observed in two hysterectomized animals and in two animals with intra-uterine implants of indomethacin.

Animals↗

PubMed1983

Plasma concentrations of progesterone, oestradiol-17 beta and 13,14-dihydro-15-oxo-prostaglandin F2 alpha in the pregnant wallaby (Macropus rufogriseus rufogriseus).

The concentrations of progesterone and oestradiol-17 beta in the maternal plasma of Bennett's wallaby, Macropus rufogriseus rufogriseus, were measured daily throughout gestation after reactivation of the diapausing corpus luteum by removal of the suckling pouch young (RPY). Progesterone increased from mean concentrations of 382-424 pmol/l (120-133 pg/ml) during lactation to reach peak concentrations of 908 +/- 172 (S.E.M.) pmol/l (285 +/- 54 pg/ml) (n = 8) 4 days after RPY and 971 +/- 220 and 971 +/- 229 pmol/l (305 +/- 69 and 305 +/- 72 pg/ml) (n = 7) 24 and 25 days after RPY respectively. The mean gestation length (RPY to birth) was 26.8 +/- 0.6 (S.D.) days (n = 6, range 25.75-27.50 days). Immediately after birth the plasma progesterone concentration declined to 299 +/- 51 (S.E.M.) pmol/l (94 +/- 16 pg/ml) (n = 6). Oestradiol-17 beta increased from mean concentrations of 291-553 pmol/l (80-152 pg/ml) during lactation to reach a peak concentration of 967 +/- 331 pmol/l (266 +/- 91 pg/ml) (n = 9) 1 day after RPY. The concentration declined from 7 days after RPY and fluctuated between mean concentrations of 273 and 480 pmol/l before reaching a minimum of 207 +/- 69 pmol/l (57 +/- 19 pg/ml) (n = 6) 19 days after RPY. A transient increase to 542 +/- 207 pmol/l (n = 7) occurred at 22 days after RPY. Plasma concentrations declined to a low of 156 +/- 55 pmol/l (43 +/- 15 pg/ml) (n = 6) 5 days after parturition. The mean concentration of plasma 13,14-dihydro-15-oxo-prostaglandin F2 alpha was less than 2.8 nmol/l (1 ng/ml) for all samples from 13 days after RPY until 4 days after parturition. The results suggest that oestradiol-17 beta may be important in the early stages of blastocyst reactivation to synergize with progesterone in stimulating uterine secretions. 13,14-Dihydro-15-oxo-prostaglandin F2 alpha is unlikely to be involved in the birth process and any luteolytic effect is likely to be from a local production of PGF2 alpha.

Animals↗

PubMed1992

Prostaglandin F2 alpha- and phorbol 12-myristate-13-acetate-stimulated progesterone production by cultured human luteal cells in the mid-luteal phase: prostaglandin F2 alpha increases cytosolic Ca2+ and inositol phosphates.

While prostaglandin F2 alpha (PGF2 alpha) has been thought to be a natural luteolysin in non-primates, a luteolytic effect in the human corpus luteum is less evident. We therefore investigated the action of PGF2 alpha on monolayer cultures of human luteal cells obtained from mid-luteal phase corpora lutea. PGF2 alpha increased basal and human chorionic gonadotrophin (hCG)-stimulated progesterone production by human cultured luteal cells. A potent tumour-promoting phorbol ester, phorbol 12-myristate-13-acetate (PMA), also stimulated progesterone production by cultured human luteal cells. Although human luteal cells were incubated for 24 h with PMA, hCG was still able to stimulate the production of progesterone by PMA-pretreated cells. However, PMA pretreatment blocked the ability of PGF2 alpha to stimulate progesterone production. It is possible that the luteotrophic effect of PGF2 alpha may be mediated, in part, by the activation of protein kinase C. Addition of PGF2 alpha to suspensions of human luteal cells preincubated with myo-[2-3H]inositol promoted an increase in labelled inositol phosphates. PGF2 alpha also rapidly increased intracellular free Ca2+ in human luteal cells loaded with the fluorescent Ca2+ probe, fura-2. We conclude that PGF2 alpha and PMA stimulate progesterone production and that PGF2 alpha increases the intracellular free calcium and inositol phosphates of human cultured luteal cells in the mid-luteal phase.

Calcium↗

PubMed1999

Gonadotropin-releasing hormone agonist has the ability to induce increased matrix metalloproteinase (MMP)-2 and membrane type 1-MMP expression in corpora lutea, and structural luteolysis in rats.

Gonadotropin-releasing hormone (GnRH) and its agonist analog (GnRHa) are well known to have luteolytic effects. We previously reported that prolactin (PRL) stimulated matrix metalloproteinase (MMP)-2 activity to degrade collagen type IV as a mechanism of structural luteolysis. The effects of GnRHa treatment on developed corpora lutea are unknown. In this study we assessed the effect of GnRH on MMP expression and induction of structural involution of developed corpora lutea of superovulated rats using GnRHa. Pregnant mare serum gonadotropin-human chorionic gonadotropin (hCG)-synchronized ovulation and luteinization were induced in immature female rats, followed by daily treatment with GnRHa from 5 days after hCG treatment. GnRHa-induced involution of corpora lutea was evident 3 days after the treatment, as shown by their markedly smaller size (60% of the control weight). Nine days after hCG injection, serum progesterone and 20alpha-dihydroprogesterone concentrations were as low as those associated with structural luteolysis. These findings revealed that GnRHa has the ability to induce structural luteolysis in superovulated rats in the same way that PRL does. To gain information on mechanisms of luteal involution induced by GnRHa, we performed gelatin zymography. This showed a significant increase in the active form of MMP-2 in the luteal extract of GnRHa-treated rats (more than twofold that of the control). Activation of pro-MMP-2 by membrane type-MMP (MT-MMP) is reported to be a rate-limiting step for catalytic function. Another function of MT-MMP is to degrade collagen types I and III. The plasma membrane fraction of corpora lutea of GnRHa-treated rats activated pro-MMP-2 of fetal calf serum, resulting in a marked shift of the 68-kDa band to the 62-kDa band in the zymogram. A Northern hybridization study also revealed simultaneous significant increases in expression of MMP-2 mRNA and MT1-MMP mRNA in corpora lutea of GnRHa-treated rats (more than threefold the control level). In summary, hormonal and histological features of corpora lutea of GnRHa-treated superovulated rats correspond to those of structural luteolysis. GnRHa stimulated the expression of MMP-2 and MT1-MMP in developed corpora lutea associated with involution. These findings support the conclusion that MMP-2, activated by MT1-MMP, and MT1-MMP itself, remodel the extracellular matrix during structural luteolysis induced by GnRHa.

Analysis of Variance↗

PubMed2001

Prostaglandin receptors and role of G protein-activated pathways on corpora lutea of pseudopregnant rabbit in vitro.

Studies were conducted to characterize receptors for prostaglandin (PG) F(2alpha) (PGF(2alpha)) and PGE(2), and the signalling pathways regulating total nitric oxide synthase activity and progesterone production in rabbit corpora lutea (CL) of different luteal stages. CL were obtained at days 4, 9 and 13 of pseudopregnancy and cultured in vitro for 2 h with PGF(2alpha) or PGE(2) and with activators and inhibitors of G protein (Gp), phospholipase C (PLC), protein kinase C (PKC), adenylate cyclase (AC) and protein kinase A (PKA). High affinity PGF(2alpha) receptor (K(d)=1.9+/-0.6 nM mean+/-s.e.m. ) concentrations increased (P< or =0.01) four- to five-fold from early to mid- and late-luteal phases (50.6+/-8.5, 188.3+/-36.1 and 231.4+/-38.8 fmol/mg protein respectively). By contrast, PGE(2) receptor (K(d)=1.6+/-0.5 nM) concentrations decreased (P< or =0.01) from day 4 to day 9 and 13 (27.5+/-7.7, 12.4+/-2.4 and 16.5+/-3.0 fmol/mg protein respectively). The Gp-dependent AC/PKA pathway was triggered only on day 4 CL, mimicking the PGE(2) treatment and increasing progesterone production. In both day 9 and day 13 CL, the Gp-activated PLC/PKC pathway evoked a luteolytic effect similar to that induced by PGF(2alpha). The time-dependent selective resistance to PGF(2alpha) and PGE(2) by rabbit CL is mediated by factors other than a lack of luteal receptor-ligand interactions.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1993

Responsiveness of porcine large and small luteal cells to luteotropic or luteolytic hormones and cell morphologic changes during the estrous cycle and pregnancy.

Isolated porcine luteal cells from d 10 and 15 of the estrous cycle (estrus = d 0) were incubated with or without combinations of FSH (0, 10, 10(2), 10(3) ng), LH (0, 10, 10(3) ng), oxytocin, or prostaglandin F2 alpha (PGF2 alpha) (each at 0, 10, 10(3), and 10(5) pg). Progesterone (P4) content was determined after overnight incubation (0 h) then at 2 and 24 h of incubation. The basal (0 h) P4 production of large cells (LC) from d 10 corpora lutea (CL) was 31-fold higher than that by small cells (SC) at 0 h. The LC and SC from d 10 but not those from d 15, were stimulated to a small extent by LH (P < .05). The FSH inhibited P4 production (P < .05) by SC at 24 h on d 10 and by LC after 2 or 24 h of incubation on d 15. There was no interaction between LH and FSH on P4 production. Oxytocin and PGF2 alpha decreased P4 production by d 15 LC at 2 h of incubation (P < .05) and by d 15 SC after 2 or 24 h of incubation (P < .05 and P < .01). The morphology of cells from CL of the cycle or early or mid pregnancy were examined using scanning and transmission electron microscopy (EM). Freshly isolated LC (using scanning EM) from d 10 contained many microvilli arranged in apparent networks on their membranes, but SC had smooth surfaces and contained only a few microvilli. Internally, LC had more small mitochondria than did SC and a different organization of smooth endoplasmic reticulum (SER). The SC from CL of pregnant (d 30 to 60) gilts contained more mitochondria than SC from CL of cyclic gilts. The results indicate that FSH, oxytocin, and PGF2 alpha can have a direct cellular luteolytic effect in the late luteal phase in pigs. The FSH influenced LC, whereas oxytocin and PGF2 alpha effected a more pronounced decrease in P4 from SC. The lower amount of P4 produced overall by SC may be associated with fewer microvilli, mitochondria, and SER in SC.

Animals↗

PubMed1986

Maintenance of the corpus luteum of early pregnancy in the ewe. IV. Changes in luteal sensitivity to prostaglandin F2 alpha throughout early pregnancy.

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)

Animals↗

PubMed1987

Trial of 17-hydroxyprogesterone caproate (Proluton Depot) in women with long-standing infertility; failure of estrogen positive feedback the following cycle.

In open and double-blind studies 40 women with long-standing unexplained infertility were investigated and treated with 17 alpha-hydroxyprogesterone caproate (17HPC, Proluton Depot). In the open study, 16 women with a high index of suspicious abortions were given 500 mg 17HPC imtramuscularly (i.m.) weekly for 6-16 weeks. Six of the women received the drug from a time preceding the expected date of a period; 2 of these conceived that cycle and their pregnancies continued to term, while 4 were not pregnant. Ten women (9 with definite previous abortions) were given 17HPC when they suspected (correctly) that they were pregnant. Their pregnancies continued to term in all but 1, who had a premature delivery (still-birth) at 34 weeks. In the double-blind study 24 women were given injections of 17HPC or placebo i.m. at weekly intervals, from about 4 days before the expected period (day -4), provided that the level of progesterone (Prog) (on days -9 to -7) was greater than 10 nmol/l. After placebo no delay in menstruation or disruption of the succeeding cycle was observed. In 14 of 16 cycles in 14 women given 500 mg 17HPC the withdrawal period was delayed by a few days, and then followed by highly erratic bleeding over the next 1-3 months. The dose was therefore reduced to 250 mg 17HPC but the same problem resulted in 8 of 29 cycles in 16 women (including the above studied in later cycles). Regular cycles were eventually restored in all cases but in 3 this necessitated treatment with the contraceptive pill (Microgynon). In most of the post-treatment cycles there was a progressive and prolonged estradiol (E2) rise, which was not preceded by changes either in serum FSH concentration or in the LH/FSH ratio nor associated with the expected positive feedback rise in LH. We conclude that 17HPC disrupts the following cycle, probably by allowing follicular development while interfering with positive LH feedback. None of the patients of the double-blind study had conceived (as evidenced by undetectable hCG levels). Our study confirmed that this progestogen exerts no direct luteolytic effect. However, in order to establish the efficacy or otherwise of 17HPC given before the end of the cycle, women should be selected with a very high index of suspicion of recurrent early implantation failure or abortion.

17 alpha-Hydroxyprogesterone Caproate↗

PubMed1975

Oestrus, ovulation and plasma hormones after prostaglandin F2alpha in mares.

The luteolytic effect of PGF2alpha, administered by intrauterine infusion or subcutaneous injection during early dioestrus, was observed in mares of mixed breeds. An infusion of 10 mg on Days 7 to 9 after ovulation caused a sharp fall in plasma progesterone levels and induced oestrus and ovulation. Oestrus was significantly longer than in the natural cycle but the time of ovulation in relation to the end of oestrus was normal. The time of return to oestrus following luteolysis was not dependent on the amount of PGF2alpha within the range of doses given. Luteolysis could be induced as early as Day 5 following natural ovulation.

Androstenedione↗

PubMed1975

Adequacy of main uterine vein and the ovarian artery in the local venoarterial pathway for uterine-induced luteolysis in ewes.

The local uteroovarian pathway for uterine-induced luteolysis was studied in 34 ewes. Bilaterally ovulating ewes were used to study the role of the main uterine vein (uterine branch of uteroovarian vein) and unilaterally ovulating ewes were used to study the role of the ovarianartery. Surgical operation was done on day 7, 8, or 9 of diestrus and ewes were necropsied on day 20. In 4 bilaterally ovulating control ewes (unilaterally hysterectomized), mean weight of corpus luteum (CL) was less (P smaller than 0.05) on the side of the intact uterine horn (55 mg) than on the side of unilateral hysterectomy (548 mg). In 4 treated ewes (unilaterally hysterectomized and with surgical anastomosis of uterine vein from the intact side to the hysterectomized side), mean weight of CL on the hysterectomized side (153 mg) was less (P smaller than 0.05) than on the uterine-intact side (391 mg). The mean weight of CL on the hysterectomized side in the treated group was not significantly different from that of the uterine-intact side in the control group. Unilaterally ovulating ewes were randomized into 5 groups: (1) controls which were uterine intact, (2) controls in which a unilateral hysterectomy was done ipsilateral to CL, (3) unilateral hysterectomy done ipsilateral to CL and anastomosis of the ovarian branch of the ovarian artery on the uterine-intact side to the ovarian branch of the ovarian artery on the hysterectomized side, (4) controls in which unilateral hysterectomy was done contralateral to CL and the ovarian vascular pedicle on the uterine-intact side was isolated, and (5) unilateral hysterectomy done contralateral to CL, isolation of ovarian vascular pedicle on the uterine-intact side, and anastomosis of the ovarian branch of the ovarian artery on the unilaterally hysterectomized side to the ovarian branch of the ovarian artery on the uterine-intact side. Mean weight of CL was less (P smaller than 0.05) in groups 1 (56 mg), 3 (40 mg), and 4 (120 mg) than in groups 2 (408 mg) or 5 (473 mg). The mean weight of CL was not significantly different among groups 1, 3, and 4 or between groups 2 and 5. Results demonstrate that the local luteolytic effect of the uterus in ewes involves a venoarterial pathway and indicate that the main uterine vein is an adequate uterine outlet and the ovarian artery is an adequate ovarian inlet for the venoarterial pathway without the necessity of other possible concomitant local routes.

Animals↗

PubMed1975

[Indications for prostaglandins in the field of reproduction in farm animals (author's transl)].

Parenteral administration of 2.5-5 mg. of prostaglandin F2alpha to horses, 15 mg. to heifers or 25-30 mg to lactating cows and 15 mg. to sheep will induce regression of the corpus luteum (luteolysis) and a fertile oestrus within 48-72 hours. Because of their luteolytic effect prostaglandins may be used in various indications in the field of reproduction. An exception is the pig in which administration of prostaglandins does not induce luteolysis before D12 and therefore fails to induce oestrus. In horses, cattle and sheep, administration of prostaglandins during the first four days of the cycle is ineffective. In the present paper, a few indications for the use of prostaglandins are described, including induction of oestrus (in cases of suboestrus), synchronisation of oestrus, termination of unwanted gestation, elimination of a persistent corpus luteum (purulent endometritis, pyometra, mummified foetus), induction of parturition. In addition, some other indications are listed, such as reduction of the interval between parturition and conception, chronic endometritis, hydroallantois, luteinized cysts and suboestrus post weaning. In the opinion of the present authors, the most important field for the use of prostaglandins will be that of induction and synchronisation of oestrus. As regards the fertility of synchronized oestrus induced by prostaglandins, it is stated that, in cattle and horses, this is superior to that following treatment with progestagen. Extensive field trials will be required to determine whether the fertility of oestrus induced by prostaglandins is equivalent to that following spontaneous oestrus.

Animals↗