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PubMed2002

Effects of dose and route of administration of cloprostenol on luteolysis, estrus and ovulation in beef heifers.

Four experiments were conducted (with crossbred beef heifers) to determine the effects of dose and route of administration of cloprostenol on luteolysis, estrus and ovulation. In Experiment 1, 19 heifers with a CL > or = 17 mm in diameter were randomly allocated to receive cloprostenol as follows: 100 microg s.c., 250 microg s.c., or 500 microg i.m. Heifers given 100 microg s.c. had a longer (P<0.03) interval (120.0 h+/-10.7 h; mean+/-S.E.M.) from treatment to ovulation than those given either 250 microg s.c. or 500 microg i.m. (92.0 h+/-7.4 h and 84.0 h+/-8.2 h, respectively). In Experiment 2, 28 heifers were given porcine LH (pLH), followed in 7 days by cloprostenol (same doses and routes as in Experiment 1), and a second dose of pLH 48 h after cloprostenol. Luteolysis occurred in all heifers, and no difference was detected among treatment groups in the interval from cloprostenol treatment to ovulation (mean, 101 h; P<0.9). In Experiment 3, 38 heifers at random stages of the estrous cycle (but with plasma progesterone concentrations > or =1.0 ng/ml) received 500 or 125 microg cloprostenol by either i.m. or s.c. injection (2/2 factorial design). There was no difference (P<0.4) among groups in the proportions of heifers that were detected in estrus or that ovulated. However, the interval from cloprostenol treatment to estrus was shorter (P<0.02) in the group that received 500 microg i.m. (58.5h) than in the other three groups (500 microg s.c., 75.0 h; 125 microg i.m., 78.0 h; and 125 microg s.c., 82.3h). In Experiment 4, 36 heifers were treated (as in Experiment 3) on Day 7 after ovulation. The proportions of heifers detected in estrus and ovulating after 125 microg s.c. (33 and 44%, respectively) or 125 microg i.m. (55 and 55%) were lower (P<0.05) than in those that received 500 microg s.c. (100 and 100%), but not different from those receiving 500 microg i.m. (78 and 89%, respectively). Overall, ovulation was detected in 9/18 heifers given 125 microg and 17/18 heifers given 500 microg of cloprostenol, on Day 7 (P<0.01) and was detected in 17/20 heifers given 125 microg and 18/18 heifers given 500 microg of cloprostenol, at random stages of the estrous cycle (P>0.05). Although there was no significant difference in luteolytic efficacy between i.m. and s.c. injections of the recommended dose (500 microg) of cloprostenol, variability in responsiveness to a reduced dose depended upon CL sensitivity, therefore, reduced doses cannot be recommended for routine use.

Animals↗
PubMed1997

Alterations in follicular maturation associated with within-breed variation in ovulation rate in Chios sheep.

Within-breed comparisons may be helpful to identify, in a given genetic background (Chios sheep), ovarian strategies and control mechanisms associated with altered ovulation rate. High and low ewes were identified from two large groups (n = 27 and n = 33 in Exp. 1 and Exp. 2 respectively) of Chios ewes submitted to repeated laparoscopies (24 times in Exp. 1 and six times in Exp. 2). High ovulatory ewes (n = 6 and n = 7 in Exp. 1 and Exp. 2 respectively) had mean ovulation rates of 4.3 (Exp. 1) and 4.2 (Exp. 2) while low ovulatory ewes (n = 6 and n = 7 in Exp. 1 and Exp. 2 respectively) had mean ovulation rates of 2.5 (Exp. 1) and 1.9 (Exp. 2). In Exp. 1, follicular function was compared in these two groups of ewes using follicles obtained at 30 h following luteolysis in the same ewes before and after unilateral ovariectomy (ULO). In Exp. 2, circulating follicle stimulating hormone (FSH) concentrations were measured from the end of the luteal phase up to the preovulatory surge in high and low ewes. Thereafter, to demonstrate a causal link between high FSH and high ovulation rate, pituitary downregulation was achieved by a 17-day gonadotrophin releasing hormone (GnRH) agonist treatment and the ovarian response to similar amounts of exogenous gonadotrophins compared between high and low ewes. Numbers of oestrogenic (in vitro oestradiol > 250 pg ml-1 h-1) follicles on the first ovary removed (Exp. 1) were 2.16 +/- 0.5 vs. 1.33 +/- 0.17 in high and low ewes (P = 0.1). Following ULO, these numbers were 3.33 +/- 0.33 and 2.5 +/- 0.18 (P < 0.05 between high and low ewes). There were no significant differences between the first and second ovaries for any of the parameters studied. Follicles from high ovulatory ewes (n = 33) differed from those of low ovulatory ewes (n = 23) by a smaller size (P < 0.01), a reduced number of granulosa cells (P < 0.01) together with decreased oestradiol (P < 0.05) and testosterone (P < 0.01) production in vitro. However, steroid production per cell (oestradiol per granulosa cell, testosterone per thecal cell) was similar in the two groups of sheep. FSH concentrations (Exp. 2) in high ovulatory ewes were significantly higher than those of low ovulatory ewes during the late luteal phase, and the decrease in FSH concentrations was steeper (1.4 ng) during the early follicular phase for high ovulatory ewes than low ovulatory ewes. Chemical hypophysectomy achieved by a 17-day treatment with a GnRH agonist demonstrated that these high FSH concentrations may be important to generate the high ovulation rate of the 'high' ewes as ovulation rate of high and low ewes was similar following chemical hypophysectomy followed by administration of similar amounts of exogenous gonadotropins to both groups of ewes. It is concluded that, despite different genetic control of their high ovulation rate (Chios-polygenic; Booroola-major gene), alterations in follicular function and its control are very similar in high ovulatory Chios and in FecB carriers.

Analysis of Variance↗
PubMed1997

Vaginal temperature is not related to the time of ovulation in sows.

The relationship between vaginal temperature and ovulation time was studied in sows. The vaginal temperature was measured continuously between Day 4 and Day 10 after Altrenogest-treatment in 10 sows. Oestrus was checked with a vasectomized boar at 8-h intervals, and during oestrus, ovulation time was checked with transrectal ultrasonography at 2-h intervals between 07:00 h and 23:00 h. Two sows ovulated between 23:00 h and 07:00 h, and these sows were taken out of the experiment. In the eight remaining sows, a clear day/night rhythm in vaginal temperature was found: between 03:00 h and 09:00 h, vaginal temperature (LSM +/- sem, corrected for sow) was on average 38.2 +/- 0.01 degrees C; between 15:00 h and 21:00 h, vaginal temperature was on average 38.5 +/- 0.01 degrees C (P < 0.001). Between 4 days before ovulation and 2 days after ovulation, no changes in temperature could be found that were related to ovulation time in any of the sows. Therefore, in sows, changes in vaginal temperature cannot be used as a predictor for ovulation time, and consequently cannot be used to predict the best time for insemination.

Animals↗
PubMedDate not supplied

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) blocks ovulation by a direct action on the ovary without alteration of ovarian steroidogenesis: lack of a direct effect on ovarian granulosa and thecal-interstitial cell steroidogenesis in vitro.

The main purpose of this study was to investigate the direct effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on ovarian function including ovulation and steroidogenesis. In vivo effects of TCDD were investigated on ovulation and alteration of circulating and ovarian steroid hormones in immature hypophysectomized rats (IHR) primed with equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). In addition, in vitro effects of TCDD on the steroidogenesis of granulosa cells (GC), theca-interstitial cells (TIC), and whole ovarian dispersates derived from the ovary of IHR were investigated. In the ovulation model, rats were hypophysectomized on Day 23 of age. On Day 26, the IHR were given 20 microg TCDD/kg by gavage. The next day eCG (10 IU) was injected sc to stimulate follicular development. Fifty-two hours after eCG, 10 IU hCG was given to induce ovulation. TCDD (20 microg/kg) blocked ovulation and reduced ovarian weight in IHR. Concentrations of progesterone (P4), androstenedione (A4), and estradiol (E2) in sera and ovaries were not altered by TCDD at 12, 24, 48, and 72 h after eCG. except for a two-fold increase in ovarian concentration of A4 at 48 h after TCDD. However, this higher concentration of A4 at 48 h after TCDD did not reflect that of A4 in sera and did not correlate with E2 in either sera or ovaries. In isolated GC from untreated IHR, TCDD (0.1 to 100 nM) had no significant effect on P4 and E2 after stimulation by LH or FSH. In TIC and whole ovarian dispersates containing GC, TIC, and other ovarian cells, TCDD (0.1 to 800 nM) had no effect on A4 and P4 secretion stimulated by LH. Using RT-PCR, AhR mRNA was shown to be expressed constitutively in the whole ovary of IHR with maximum down-regulation at 6 h after TCDD (20 microg/kg). Ovarian CYP1A1 was induced maximally at 6 h after TCDD, whereas CYP1B1 could not be detected. The induction of AhR related genes by TCDD in the ovary implies the existence of AhR-mediated signal transduction pathways. In summary, these results indicate that TCDD does not affect ovulation in IHR by altering ovarian steroidogenesis. It seems that inhibition of ovulation by TCDD is due to processes related to follicular rupture.

Animals↗
PubMed2001

Effects of carbamazepine on the first ovulation in gonadotropin-primed immature female rats.

1. The effects of carbamazepine (CBZ) and its possible mechanisms on the first ovulation were investigated in immature female rats. The first ovulation was induced by administration of equine chorionic gonadotropin (eCG) at 0800 h at 26 days of age. 2. A single s.c. injection of 360 mg x kg(-1) CBZ at 1300 h on the first pro-oestrus (day 28) completely inhibited the first ovulation on the morning of day 29. A marked elevation in 13, 14-dihydro-prostaglandin F2alpha (13, 14H2-PGF2alpha) forming capacity, a sensitive indicator of luteinizing hormone (LH) surge, was not detected in the CBZ-treated group at 0800 h on day 29 (72 h after eCG treatment). The elevation in serum LH levels at 57 h after eCG treatment was not observed in the CBZ-treated group, either. The blocking of the first ovulation and 13, 14H2-PGF2alpha forming capacity were recovered by an i.p. injection of human CG on day 28 in all animals. 3. However, the first ovulation was not blocked by repeated injections of 360 mg x kg(-1) CBZ at 1300 h once daily for 3 days (days 26 - 28). The repeated injections of CBZ caused a great fall (64% decrease) in the serum levels of CBZ at 4 h after the final CBZ injection as compared with the case of a single injection of CBZ and resulted in a delay for 5 h the occurrence of LH surge, which is normally observed around 57 h after eCG injection. 4. A significant increase in the activity of microsomal CBZ catabolism by the repeated injections of CBZ was quantitatively verified by the HPLC analysis. But, the activity of CBZ metabolism in the single injected-animals showed almost similar levels to that in the control. 5. The present results demonstrated that a single injection of CBZ blocks the ovulation by inhibiting LH surge but that the failure of the inhibition of ovulation by repeated injections of CBZ is due to a decrease in serum CBZ levels mediated through CBZ-induced hepatic enzyme induction.

Animals↗
PubMed2003

Characteristics of the best prognostic evidence: an example on prediction of outcome after clomiphene citrate induction of ovulation in normogonadotropic oligoamenorrheic infertility.

The standard first-line treatment for normogonadotropic anovulatory infertile patients [referred to as World Health Organization group 2 (WHO 2)] is ovulation induction using clomiphene citrate (CC) in incremental doses. Twenty to 25% of women show clomiphene-resistant anovulation (CRA), that is, they remain anovulatory even after multiple attempts with increased doses of CC. About 50% of the ovulatory CC patients conceive within six CC-induced cycles. Given the heterogeneous nature of the group, the individual prognosis (i.e., the chance of success) will vary considerably between patients. In the event an individual prognosis of each patient would be available before the start of the treatment, the overall efficiency of ovulation induction could be improved. Prognostic evidence at an individual level should use multiple patient variables, including results from previous treatments (if any). When variables are interdependent, a statistical model can be used to relate individual characteristics with the predicted outcome. Such a model will provide estimates of prognosis for individualized patient profiles, allowing new patients to profit from the experience of the cohort of previous patients used to build the model. This paper discusses the prediction of time to pregnancy following induction of ovulation with CC. This prediction was broken down in two steps, leading to two separate prognostic models. The first model predicts an intermediate outcome, the chance that the patient will be CRA (i.e., no ovulation in response to CC medication); the second model predicts the final outcome (time until pregnancy) in women who do ovulate. The CRA model was based on a prospective cohort study of 201 patients with normogonadotropic oligoamenorrheic infertility, 45 of whom were CRA (22%). It contained four predictor variables all related to the diagnosis of PCOS within the group of WHO 2: Increased free androgen index (FAI; hyperandrogenemia), elevated body mass index (BMI; obesity), greater mean ovarian volume (as an ultrasound feature of polycystic ovaries), and amenorrhea were all predictive for CRA. The second model was based on the non-CRA patients and contained two prognostic variables: increased age and oligomenorrhea were predictive for longer time to pregnancy after first ovulation with CC. Using the example of the prediction of time to pregnancy following induction of ovulation with CC, we present and discuss characteristics of good prognostic evidence for clinical use, focusing on study design, statistical analysis, evaluation, and presentation of results.

Amenorrhea↗
PubMed1986

The influence of continuous intrauterine infusion of enzyme-inhibitors of the arachidonic acid cascade on ovulation and tubal ovum transport in the hyperstimulated rabbit.

Cyclo-oxygenase and prostaglandin-15-hydroxydehydrogenase are rate-limiting steps in the arachidonic acid cascade. These enzymes were affected by indomethacin and lonazolac treatment in hyperstimulated rabbits through continuous intrauterine or single vaginal applications in three different experiments. In terms of the ovulation-index, there was no difference between animals treated via the intrauterine or the vaginal routes. Compared with controls (83 to 89%), there was a significant reduction in the ovulation index to 32% with indomethacin and to 51 or 55% with lonazolac, 28 h after induction of ovulation (experiment 1). The values turned almost back to normal 52 h after induction of ovulation 72% (experiment 3). The treatment with lonazolac resulted in a higher sum of corpora lutea and unruptured follicles (experiment 1: control-group = 90.9 vs lonazolac-group = 110.5). The recovered ova showed a shift from the 4 and 8 cell stages to the 16 or more cell stages under lonazolac treatment when compared with controls (experiment 3). The histologic examinations showed advanced luteinization of unruptured follicles in the indomethacin-treated groups. Hyperplasia of the theca interna was also noted. Our data indicate that indomethacin was capable of inducing premature luteinization resulting in arrested or delayed ovulation. Lonazolac, in contrast, did not impair ovulation. Moreover, it induced the growth of more follicles, probably through a second wave at the time of ovulation initiated by hCG. For the clinical practice these experiments point towards the possibility of the treatment of the luteinized unruptured follicle syndrome and towards the application of lonazolac for ovarian stimulation.

Animals↗
PubMed2001

Genetic mutations influencing ovulation rate in sheep.

Ovulation rate in mammals is determined by a complex exchange of endocrine signals between the pituitary gland and the ovary, and by paracrine signals within ovarian follicles between the oocyte and its adjacent somatic cells. One approach to identifying factors regulating ovulation rate is to find mutations that influence the target phenotype and, in this context, sheep are proving to be remarkable experimental models. Recently, in three sheep families, namely Inverdale, Hanna and Booroola, the inherited mutation was mapped to a specific region of the sheep X chromosome (Inverdale, Hanna) or sheep chromosome 6 (Booroola) and in each, a point mutation was identified in genes from the bone morphogenetic protein (BMP) relatives of the transforming growth factor beta superfamily or their receptors. In Inverdale (I) and Hanna (H) sheep, separate point mutations were identified in the BMP15 gene corresponding to sites in the mature peptide coding region of the BMP15 growth factor (also known as growth differentiation factor 9B; GDF9B). Expression of the BMP15 gene was located exclusively in oocytes from the primary stage of follicular growth. There is a complete block of normal follicular development in females carrying two copies of the Inverdale mutation (II), two copies of the Hanna mutation (HH), or one copy of each mutation (HI). Increased ovulation rates are found in females with only one copy of either mutation (I+ or H+). In Booroola sheep, a point mutation was identified in the highly conserved intracellular serine threonine kinase signalling domain of the BMP-1B receptor. Within the ovary, this gene is expressed in oocytes in primordial and pre-antral follicles and in granulosa cells from the primary stage of growth as well as in corpora lutea. The effect of the Booroola mutation is additive for ovulation rate: animals with one copy of the mutation have an ovulation rate of 3 or 4, whereas those with two copies have an ovulation rate of between 5 and 14. Physiological studies of the above mutations demonstrate that the oocyte plays an active role with respect to its adjacent somatic cells during follicular development and support the hypothesis that the oocyte has a significant influence on the number of follicles that proceed to ovulation.

Animals↗
PubMed1993

Relationship between clustering of post-ovulatory and hierarchical follicles and their order of ovulation in the mature domestic hen (Gallus gallus domesticus).

Hierarchical (> 8 mm) and post-ovulatory follicles from the ovaries of laying hens at 45 and 86 weeks of age were assigned to clusters defined by the coalescence of their follicular stalks. They were also classified by size to give the succession in which ovulation had occurred, or would occur for the hierarchical follicles. The association between the order of ovulation and the observed clusters was compared with randomness and with dependence on the cluster in which the immediately preceding ovulation occurred. The order of ovulation was associated randomly with clusters, and was independent of the cluster containing the preceding ovulation. Many perceived clusters of successive follicles and post-ovulatory follicles may be compatible with a random order of ovulation. These findings do not support theories of stimulation or inhibition of adjacent follicles, leading to eventual ovulation, by a dominant follicle.

Aging↗
PubMed1995

Ovulation efficiency is reduced in mice that lack plasminogen activator gene function: functional redundancy among physiological plasminogen activators.

Several lines of indirect evidence suggest that plasminogen activation plays a crucial role in degradation of the follicular wall during ovulation. However, single-deficient mice lacking tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), or PA inhibitor type 1(PAI-1) gene function were recently found to have normal reproduction, although mice with a combined deficiency of tPA and uPA were significantly less fertile. To investigate whether the reduced fertility of mice lacking PA gene function is due to a reduced ovulation mechanism, we have determined the ovulation efficiency in 25-day-old mice during gonadotropin-induced ovulation. Our results reveal that ovulation efficiency is normal in mice with a single deficiency of tPA or uPA but reduced by 26% in mice lacking both physiological PAs. This result suggests that plasminogen activation plays a role in ovulatory response, although neither tPA nor uPA individually or in combination is obligatory for ovulation. The loss of an individual PA seems to be functionally complemented by the remaining PA but this compensation does not appear to involve any compensatory up-regulation. Our data imply that a functionally redundant mechanism for plasmin formation operates during gonadotropin-induced ovulation and that PAs together with other proteases generate the proteolytic activity required for follicular wall degradation.

Animals↗
PubMed2000

Prediction of ovulation by urinary hormone measurements with the home use ClearPlan Fertility Monitor: comparison with transvaginal ultrasound scans and serum hormone measurements.

The timing of sexual intercourse in relation to ovulation strongly influences the chance of conception. Daily serum LH measurements or transvaginal ultrasonography are not practical to determine ovulation in consecutive cycles for an individual. A prospective study was initiated to test the home use performance of the ClearPlan Fertility Monitor (CPFM) in ovulation prediction compared with transvaginal ultrasonography and serum hormone measurements. A total of 53 women aged 18-39 years with a normal uterus and at least one ovary, cycle length between 21-42 days and not using medication which interferes with ovarian function contributed 150 cycles for analysis. One cycle was anovulatory and no LH surge, indicating peak fertility, was detected by the monitor. Of the remaining 149 cycles, 135 (90.6%) had a monitor LH surge and ultrasonographically confirmed ovulation. Ovulation was detected in 91.1% of cycles during the 2 days of CPFM peak fertility. Ovulation was observed in 51.1% of cycles 1 day and in 43.2% of cycles 2 days after the surge in serum LH. Ovulation never occurred before CPFM peak fertility or the serum LH surge day. CPFM can help women who desire pregnancy to time intercourse. It may also have potential as a diagnostic aid and for monitoring the treatment of infertility.

Adolescent↗
PubMed2003

High singleton live birth rate following classical ovulation induction in normogonadotrophic anovulatory infertility (WHO 2).

BACKGROUND: Medical induction of ovulation using clomiphene citrate (CC) as first line and exogenous gonadotrophins as second line forms the classical treatment algorithm in normogonadotrophic anovulatory infertility. Because the chances of success following classical ovulation induction are not well established, a shift in first-line therapy can be observed towards alternative treatment. The study aim was to: (i) reliably assess the probability of singleton live birth following classical induction of ovulation; and (ii) construct a prediction model, based on individual patient characteristics assessed upon standardized initial screening, to help identify patients with poor chances of success. METHODS: A total of 240 consecutive women visiting a specialist academic fertility unit with a history of infertility, oligomenorrhoea or amenorrhoea, and normal FSH and estradiol serum concentrations (WHO group 2) was prospectively followed. The women had not been previously treated with ovulation-inducing agents. All patients commenced with CC. Patients who did not ovulate within three treatment cycles of incremental daily doses up to 150 mg for 5 consecutive days or ovulatory CC patients who did not conceive within six cycles, subsequently underwent gonadotrophin induction of ovulation applying a step-down dose regimen. The main outcome measure was pregnancy resulting in singleton live birth. Cox regression was used to construct a multivariable prediction model. RESULTS: Overall, there were 134 pregnancies ending in a singleton live birth (56% of women). The cumulative pregnancy rate after 12 and 24 months of follow-up was 50% and 71% respectively. Polycystic ovary syndrome (PCOS) patients (49%), clearly non-PCOS patients (13%) and the in-between group did not differ in prognosis (P = 0.9). The multivariable Cox regression model contained the woman's age, the insulin:glucose ratio and duration of infertility. With a cut-off value of 30% for low chance, the model predicted probabilities at 12 months lower than this cut-off for 25 out of 240 patients (10.4%). CONCLUSIONS: Classical ovulation induction produces very good results in normogonadotrophic anovulatory infertility. Alternative treatment options may not be indicated as first-line therapy in these patients, except for subgroups with poor prognosis. These women can be identified by older age, longer duration of infertility and higher insulin:glucose ratio.

Adult↗
PubMed1987

The reliability of ovulation prediction by a single ultrasonographic follicle measurement.

Since ultrasonographic ovulation detection has been introduced many authors have speculated about the ovulation predictive value of this new technique. Reliable studies in this respect, however, are lacking. The present study describes ultrasonographic data of 158 spontaneously ovulating, infertile patients. Each patient contributed only one cycle to the study. To construct individual follicle growth curves serial follicular measurements were performed. A wide range existed in mean maximum diameters of the preovulatory follicles. Furthermore, the slopes of the follicle growth curves, as well as the durations of the follicle growth phases showed considerable variations. The intrinsic variability in the various characteristics of follicle growth makes a single measurement as accurate as serial measurements in predicting ovulation. A formula has been devised by means of the data of the first 100 women, which correlates follicular diameter with the time interval to ovulation. The formula was developed based on one randomly selected measurement per patient. The validity of the formula has been tested in 58 additional women, also contributing one measurement each. According to this validation the adequacy of the prediction rule was demonstrated. Ultrasound appeared to be a less sensitive method for prediction of ovulation than has been speculated by some investigators. It is, however, an improvement, compared to the prediction of ovulation based upon the length of the previous menstrual cycles. A single follicle measurement may therefore be helpful in timing post-coital tests or artificial inseminations, in addition to being an adjuvant to more reliable methods.

Female↗
PubMed1982

Ovarian and plasma prostaglandin E and F levels in brook trout (Salvelinus fontinalis) during pituitary-induced ovulation.

Prostaglandin E (PGE) and F (PGF) levels in plasma, ovarian tissue and coelomic fluid from ovulating brook trout (Salvelinus fontinalis) were measured using radioimmunoassays. The results demonstrate a significant increase in both plasma and ovarian PGF levels by the completion of ovulation (compared to gravid controls). Plasma PGF levels remained elevated 24 h following ovulation in females retaining ovulated eggs. Coelomic fluid from fish just completing ovulation contained PGF levels that were significantly higher than plasma PGF levels of corresponding fish. There were no significant variations in plasma PGE levels throughout ovulation; however, the ovarian PGE levels of gravid controls were significantly higher than those of fish just prior to, during or following ovulation.

Animals↗
PubMed1983

Effects of cadmium chloride on ovulation and on induction of sterility in the female golden hamster.

The effects of single subcutaneous injections of cadmium chloride (CdCl2) on ovulation, egg transport and early pregnancy in the golden hamster were studied. While a single dose of 1.25 or 2.5 mg/kg of CdCl2 imposed none to marginal effects, hamsters treated with 5 or 10 mg/kg CdCl2 experienced a period of sterility ranging from 11-69 (5 mg/kg) or 46-71 (10 mg/kg) days, followed by a normal pregnancy. Administration of CdCl2 also induced ovulation inhibition which was dose-and time-dependent. A minimum dose of 5 mg/kg CdCl2 was needed to inhibit ovulation. When CdCl2 was given closer to the time of the luteinizing hormone (LH) surge on the day of proestrus, a more pronounced effect on ovulation was recorded. The incidence of failure of ovulation was associated with decreased progesterone levels in serum and inflammation, hemorrhages and necrosis in the ovary. However, the ovarian lesions lasted less than 4 days. The results indicate that CdCl2 inhibits ovulation when administered close to the time of ovulation, whereas its influence on pregnancy is pronounced but temporary.

Animals↗
PubMed1984

Perfusion of the rat ovary in vitro: methodology, induction of ovulation, and pattern of steroidogenesis.

A method for perfusion of the rat ovary in vitro for the study of ovulation was developed and characterized. Immature rats (27-29 days old) were primed with 20 IU of pregnant mare's serum gonadotropin (PMSG). Two days later a laparotomy was performed, the aorta and vena cava were cannulated, the right ovary was isolated, and all vessels connecting with the aorta and vena cava except for the right ovarian artery and vein were ligated. The preparation was placed in the perfusion apparatus and perfused for up to 20 h with oxygenated Medium 199 containing 4% bovine serum albumin (37 degrees C, pH 7.4). The perfusion pressure was 70-90 mm Hg and the average flow was 1 ml . min . ovary. Ovulation was confirmed by oocyte recovery from the apparatus. Nine ovaries were perfused without further treatment (controls); only 1 ovulation occurred in this group. Nine ovaries received luteinizing hormone (LH; 0.1 microgram/ml) 1 h after the start of perfusion; 71 ovulations resulted (range, 3-13/ovary). Ovulations did not begin before 9 h after LH administration. Samples of medium were taken frequently for measurement of progesterone, estradiol and androstenedione. Levels of all three steroids rose rapidly and markedly in response to LH but increased only slightly in control perfusions. This study demonstrates that ovulation in the rat ovary can be induced in vitro and provides a basis for further studies on the mechanism of ovulation.

Androstenedione↗
PubMed1986

Blockade of first ovulation in pubertal rats by delta-9-tetrahydrocannabinol: requirement for advanced treatment due to early initiation of the critical period.

Successful blockade of ovulation in pubertal rats by delta-9-tetrahydrocannabinol (THC) required earlier treatment during proestrus than was required in adults under the same conditions. Only 1 of 8 adult rats ovulated after treatment with THC (10 mg/kg body weight, i.p.) at 1400 h proestrus, whereas 77% of pubertal rats released full sets of ova following similar treatment during proestrus of the first or second vaginal cycle. When treatment of pubertal rats was advanced to 1300 h, only 2 of 10 THC-treated rats exhibited full ovulation, an incidence significantly lower than the 80% ovulation rate observed in vehicle-treated animals (p less than 0.05). To determine whether the requirement for earlier THC treatment in pubertal rats was related specifically to THC or reflected possible age-associated differences in timing of the critical period, the ovulation-blocking efficacy of atropine sulfate (ATR) was tested in pubertal rats for comparison with that of THC. The serum concentrations of luteinizing hormone (LH) during the first proestrus (1200-1900 h) were determined in pubertal rats that remained untreated. The incidence of ovulation in rats treated with ATR (350 mg/kg, s.c.) at 1400 h proestrus was not significantly reduced from that in vehicle-treated rats; however, after ATR treatment at 1300 h, only 2 of 11 animals released full sets of ova whereas all vehicle-treated rats ovulated (p less than 0.025). The mean serum LH concentration in untreated pubertal rats was not significantly increased over baseline at 1300 h proestrus, but was markedly elevated by 1400 h (1009 +/- 375 ng/ml; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Interference with the preovulatory luteinizing hormone surge and blockade of ovulation in immature pregnant mare's serum gonadotropin-primed rats with the anti-androgenic drug, hydroxyflutamide.

The involvement of androgens in the control of ovulation has been assessed by administration of the androgen antagonist, hydroxyflutamide, to prepubertal rats treated with pregnant mare's serum gonadotropin (PMSG) to induce first estrus and ovulation. Without human chorionic gonadotropin (hCG) injection, only 46% of rats that received six 5-mg, s.c. injections of hydroxyflutamide at 12-h intervals, beginning an hour before s.c. injection of 4 IU PMSG on Day-2 (Day 0 = the day of proestrus), had ovulated a mean of 1.3 +/- 0.4 oocytes per rat when killed on the morning of Day 1, whereas 92% of sesame oil-treated controls had ovulated a mean of 6.9 +/- 0.6 oocytes. After i.p. injection of hCG at 1600 h on Day 0, 92% of hydroxyflutamide-treated rats ovulated a mean of 8.3 +/- 1.2 oocytes compared to 100% of controls, which ovulated 7.3 +/- 0.4 oocytes per rat: these groups were not significantly different from each other, nor from control rats that received no hCG. Thus, exogenous hCG completely overcame the inhibitory effect of hydroxyflutamide on ovulation. Rats treated with PMSG and hydroxyflutamide without hCG were killed either on the morning of Day 0 to determine serum and ovarian steroid levels or on the afternoon of Day 0 to determine serum LH levels. Serum levels of estradiol-17 beta and testosterone in hydroxyflutamide-treated rats were significantly higher (178% and 75%, respectively; p less than 0.01) than levels observed in controls on the morning of Day 0. Ovarian concentrations of the steroids were also elevated in hydroxyflutamide-treated rats (p less than 0.01 for testosterone only).(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗