Plasma binding of oestradiol in progesterone-treated rats

Progesterone treatment of female rats causes an increase in body weight possibly via suppression of oestradiol secretion. This study was carried out to investigate the effect of progesterone on the non-protein bound and hence presumably biologically active fraction of oestradiol. Oestradiol binding to plasma proteins was studied in female Wistar rats during the oestrous cycle and after 12 days of treatment with progesterone (5 mg/day). There was no change in either the unbound fraction of oestradiol or plasma albumin concentrations during the oestrous cycle. Plasma oestradiol concentrations in progesterone-treated rats were similar to those seen during dioestrus, as were the degree of oestrogen binding and the plasma albumin concentrations. Although it was not feasible to calculate unbound concentrations, these results suggest that the increased body weight seen in progesterone-treated rats, and also during pregnancy, may be a result of suppression of unbound oestradiol concentrations to levels similar to those occurring during dioestrus.     

Reproductive activities of female albino rats treated with quassin, a bioactive triterpenoid from stem bark extract of Quassia amara

To evaluate the effect of quassin on female reproductive functions, 42 albino rats (35 females and 7 males) were used. The female albino rats were divided into seven groups of five rats each. Group I served as the control group and received distilled water while Groups II, III and IV rats were treatedorally with 0.1mg/kg, 1.0 mg/kg and 2.0 mg/kg body weight of quassin for 60 days respectively. Groups V, VI and VII rats were also treated orally with 0.1 mg/kg, 1.0mg/kg and 2.0 mg/kg body weight of quassin for 60 days but were left untreated for another 30 days, to serve as the recovery groups. At the end of each experimental period, blood samples were collected from each rat. Fertility study was done by cohabiting one untreated male with the five female rats in each group for 10 days. Quassin did not adversely affect the weight of the kidney, heart, liver and the body of the rats. However there was a significant decrease in the weight of the ovary and uterus in all the groups relative to the control. There was also a significant decrease in serum estrogen levels in quassin treated rats. The quassin treated rats had a significantly decreased mean litter number and weight. Histological studies show a disorganization and degeneration in the ovary while the uterus showed signs of vacuolation and disorganization. However, these effects were ameliorated after quassin was withdrawn from the rats. The results suggest that quassin has female anti-fertility properties, possibly acting via inhibition of estrogen secretion. Keyword: Quassin, Female rat, Reproduction, Estrogen.     

Effect of pinealectomy on heat-induced endocrine changes in female rats

Exposure of pinealectomized rats to high ambient temperature (35 degrees C; PXH) brought about a diminution in pituitary weight and LH content when compared to their sham-operated peers (35 degrees C) or to pinealectomized controls (22 degrees C). Serum corticosterone level of PXH rats was significantly depressed while heat or pinealectomy alone had no effect. Mean oestrous cycle length was prolonged and blood serum progesterone was increased in the heat-exposed rats. However, the extended oestrous cycles and elevated serum progesterone levels of heat-exposed rats were depressed or abolished by pineal ablation. Thus, the pineal appears to exert a moderating effect on heat-induced endocrine changes in female rats. No changes were noticed in uterine and ovarian weights corrected for body weights either on the day of vaginal opening, at occurrence of the oestrous phase expressed as percentage of total oestrous cycle, or in N-acetyltransferase and hydroxyindole-O-methyltransferase activities.     

Effects of selenium toxicity on oestrous cyclicity, ovarian follicles, ovulation and foetal survival in rats

Effects of intraperitoneal injections of sodium selenite (2.0 and 4.0 mg/kg body weight) to normally cycling female albino Wistar rats daily for 30 days, and of single injection either during proestrous or oestrous and at each stage of the 4-day oestrous cycle were determined on oestrous cyclicity, ovarian follicles, ovulation, implantation and pregnancy outcome on day 14 of gestation. Administration of selenite for 30 days had no effect on the duration of first two oestrous cycles but afterwards the rats remained at the dioestrus stage. Their ovaries developed cystic follicles. Selenite treatments during the oestrous cycle preceding mating affects the implantation and pregnancy outcome in a dose-related manner. Its single dose containing 2.0 mg/kg body weight administered either at proestrous or oestrous, though had no effect on different reproductive parameters investigated in this study but its daily dose during the 4 day oestrous cycle reduced the number of corpora lutea and implantations as compared to saline injected control female rats. Similar effects of a single dose of selenite (4.0 mg/kg body weight) when injected at proestrous were recorded. Higher dose of selenite at oestrous or throughout the cycle decreased the number of implantations, but in addition, also increased the resorption rate/litter on day 14 of gestation. The present studies clearly show that high selenium levels in the body during the oestrous cycle preceding mating affects the number of ovulations, implantations and live embryos depending upon its dose and stage of administration.     

Female to female stimulation of ovarian activity in the ewe

The ovulatory and oestrus responses of seasonally anovulatory ewes to the presence of ewes with synchronised oestrus was evaluated. The experiment was carried between 4 June and 1 July when the ewes were in seasonal anoestrus. Two hundred adult Suffolk and Dorset ewes were used. The animals were randomly divided into five groups balanced according to breed: Group I (treated) consisted of 25 ewes induced to cycle by the treatment for 10 days with vaginal sponges containing 40 mg of fluorogestone acetate and an injection of 200 IU of pregnant mares' serum gonadotropin (PMSG) at the time of sponge removal. Group II (mixed) consisted of 25 untreated ewes housed in the same pen as the treated ewes throughout the experiment. Groups III, IV and V each consisted of 50 untreated ewes located in adjacent pens progressively more distant from the pen which contained the treated animals. The ewes in Group III had contact with the treated animals through the fence, while those in Groups IV and V were separated from the treated ewes by one and two pens respectively. Day 0 of the experiment was defined as the day in which the sponges were removed from the treated ewes. Blood samples for progesterone determination were obtained from 25 animals from each group on days 6, 10 and 13. Oestrus was detected twice a day using vasectomised rams introduced to each pen for 15 min in the morning and 15 min in the evening. As expected, the proportion of ewes with luteal activity was higher (P < 0.01) in the treated group than in the other four groups on days 6, 10 and 13. By day 13 progesterone levels were elevated in 87.5%, 52%, 37.5%, 32% and 13% of the ewes sampled in Groups I, II, III, IV and V respectively. There was a direct relationship between the proportion of non-treated ewes with ovarian activity and the intensity of contact with the treated ewes, being maximal in the ewes that remained mixed with the synchronised animals, and lowest in the ewes located in the most distant pen. The proportion of ewes that showed oestrus during the first 14 days after sponge removal was significantly higher in the treated (92%) and mixed (40%) groups than in Groups III (10%), IV (8%) and V (4%). It is concluded that the presence of a large number of ewes in oestrus can stimulate ovarian activity in seasonally anoestrous ewes. This female to female stimulation could be mediated by olfactory, visual and/or auditory stimuli.     

Influence of the oestrous cycle on L-glutamate and L-aspartate transport in rat brain synaptosomes.

Oestrous cycle and sex differences in sodium-dependent transport of L-[3H]glutamate and L-[3H]aspartate were investigated employing well washed synaptosomes prepared from rat brain cortex. Transport was best analysed on the basis of two components, a high and low affinity transport site. Oestrous cycle and sex differences were observed for both substrates. The high affinity transporter displayed highest affinity for glutamate transport in synaptosomes from female rats during proestrous and oestrous. This differed significantly from glutamate transport during dioestrous and in male rats. High affinity aspartate transport displayed highest affinity during oestrous and differed significantly from transport during dioestrous. Maximal velocity of high affinity glutamate transport was higher in synaptosomes from females during dioestrous compared with oestrous and lower in synaptosomes from male rats when compared with female rats in dioestrous and metoestrous. The low affinity sodium-dependent glutamate transporter displayed a 10-fold higher affinity for glutamate during proestrous than during the other three phases of oestrous and in male rats. Exogenously applied oestradiol and progesterone to synaptosomes from male rats showed no effect on glutamate or aspartate transport. No acute effect of oestradiol or progesterone on glutamate currents in oocytes expressing EAAT1 or EAAT2 subtype of glutamate transporter was observed. These results suggest hormonal regulation of high and low affinity sodium-dependent excitatory amino acid transporters over the four day oestrous cycle in synaptosomes from rat cortex. This regulation is unlikely to be due to a direct effect of oestradiol or progesterone on glutamate transporters.     

Response of sows to oestradiol benzoate treatment after weaning at two stages of lactation

The timing and dosage of oestradiol benzoate injected after weaning was critical with respect to the pattern of behavioural oestrus and the ovarian stimulation achieved; treatment on the day of weaning (Day 0) and Day 1 with 60 micrograms oestradiol benzoate/kg body wt produced poor ovulatory responses and abnormal oestrous behaviour. Treatment on Day 2 with 30 micrograms oestradiol benzoate/kg resulted in consistent oestrus and ovulatory responses although the ovulation rates (10 . 6 +/- 1 . 1 in 3-week and 12 . 2 +/- 1 . 7 in 5-week weaned sows) were below those expected in fertile untreated sows weaned at these times. The timing of the preovulatory LH surge (53 . 6 +/- 2 h after oestradiol benzoate) was closely synchronized in all sows and a similar synchronous rise in plasma progesterone concentrations 100 +/- 4 h after oestradiol benzoate suggests a similar synchrony of ovulation. The magnitude of the LH and FSH responses to oestradiol benzoate were similar to those that occur in untreated sows and similar differences also existed in gonadotrophin secretion related to the length of lactation.     

Effects of human chorionic gonadotrophin on contractile activity of steroid-primed pig myometrium in vitro

We examined the effects of (a) oestrogen and progesterone on concentrations of luteinizing hormone/human chorionic gonadotrophin (LH/hCG) receptors in uterine smooth muscle in vivo and (b) hCG on spontaneous myometrial contractions in vitro. Ovariectomized gilts received 2 ml corn oil (control; n = 5), 2 mg oestradiol benzoate (n = 6) or 20 mg progesterone (n = 5) for 5 days. Gilts were hysterectomized 8 h after the last injection and longitudinal sections of myometrium were incubated in modified Krebs' solution with 0 or 10 i.u. of hCG (n = 10/gilt) for 4 h at 37 degrees C in 95% O2:5% CO2. After incubation, myometrial sections were placed in a tissue chamber perfused with Krebs' solution and mechanical activity was recorded for 30 min. Cell membrane fractions were prepared from myometrial tissue not used for in-vitro studies and analysed for LH/hCG receptors. Treatment with oestradiol benzoate increased (P less than 0.01) the number of LH/hCG-binding sites compared with gilts receiving corn oil or progesterone. Incubation of myometrium with hCG reduced (P less than 0.01) the frequency and amplitude of spontaneous uterine contractions in gilts treated with oestradiol benzoate. In contrast, hCG had no effect (P greater than 0.05) on the pattern of myometrial contractions in gilts given corn oil or progesterone. These results indicate that oestradiol promotes the synthesis of LH/hCG receptors in pig myometrium and incubation of oestrogen-primed tissue with hCG has a quiescent effect on myometrial contractility.     

Effects of progesterone and oestradiol on RNA and protein metabolism in the genital tract and on survival of embryos in the ovariectomized ewe.

The hormonal regulation of metabolism in the genital tract and the development of embryos during early pregnancy in the ewe have been examined. Ovariectomized ewes received injections of maintenance progesterone, oestrous oestradiol and priming progesterone according to schedules designed to simulate endogenous ovarian secretion during early pregnancy, around the time of oestrus and during the luteal phase of the oestrous cycle immediately preceding oestrus. The survival and development of embryos was dependent upon the dose of maintenaince progesterone and the duration of treatment at the time of transfer, but changes in progesterone dose did not change endometrial protein or RNA metabolism on particular days. Both priming progesterone and oestrous oestradiol were required for normal embryo development. Priming progesterone and oestrous oestradiol each increased endometrial RNA/DNA ratios during early pregnancy. There were no interactions between priming progesterone and oestrous oestradiol, their effects being simply additive. Neither maintenance nor priming progesterone had any effect on protein and RNA metabolism in the oviduct. It is suggested that in the intact ewe oestrogen secreted at oestrus and progesterone secreted prior to oestrus play important roles in the establishment of a uterine environment suitable for the subsequent normal development of embryos.     

Zinc protection against cadmium-induced infertility in female rats. Effect of zinc and cadmium on the progesterone production of cultured granulosa cells

Adult female rats were treated subcutaneously (sc) with zinc chloride (ZnCl, 10 or 20 mg kg body weight, bw) four times during two ovarian cycles. The third injection was accompanied by cadmium chloride (CdCl) administration sc (2.5, 5 and 10 mg kg bw). The fourth zinc (Zn) treatment was followed by mating.ZnCl (20 mg kg) itself impaired fertility by 20%, while CdCl dose-dependently blocked the receptivity of female rats. In combination with 2.5 and 5 mg kg CdCl the metal salts decreased fertility in an additive fashion, whereas at the highest CdCl dose (10 mg kg) a marked ameliorating effect of ZnCl (10 and 20 mg kg) on cadmium (Cd)-caused sterility was observed.In the pregnant animals apart from the higher Cd-induced blood progesterone levels and reduced body weight gain of dams, no significant treatment-related maternal and fetal effects could be observed. ZnCl (10 to 80 m) and CdCl (10 to 80 m) were added to the culture medium of ovarian granulosa cells. CdCl suppressed follicle-stimulating-hormone- (FSH-) and cAMP-stimulated progesterone accumulation. No protective effect of Zn against Cd-induced drop in progesterone production could be seen, while Zn by itself induced a significant increase in FSH-supported progesterone synthesis.In conclusion, while Zn protected against Cd-induced sterility in vivo, it failed to counteract the direct effect of Cd on steroid biosynthesis. The data indicate that Zn protection does not take place at the level of ovary. Moreover, Zn and Cd seem to affect FSH-stimulated progesterone production by different mechanisms.     

Modification by oral contraceptives in rat of 14C acetate incorporation into platelet lipids.

The in vitro incorporation of acetate 14C in platelets lipids was compared in control female rats (Gr. I) to rats treated for 4 days either by an oral contraceptive ethinyl oestradiol + lynestrenol (Gr. II), or by ethinyl oestradiol alone (Gr. III) or lynestrenol alone (Gr. IV). An increase of 43--45% in the incorporation of acetate could be observed in the two groups (II and III) which received ethinyl oestradiol, while the incorporation in group IV was similar to that of the controls. The lipid fractions of which the synthesis was the most considerably stimulated by the oestrogen treatment, were the neutral lipids as separated from the other lipids by TLC. In groups II and III the incorporation in cholesterol and cholesterol esters was increased by 8 fold and by 10 fold in the free fatty acid fraction. In these two groups, even in the phospholipid fractions PS + PI and PE, the radioactivity was significantly increased. The observed effect of the oral contraceptive studied here on platelet lipid synthesis in female rats, appears to be essentially due to the estrogens, since lynestrenol had only minimal effects in that respect.     

Influence of estradiol and progesterone on the sensitivity of rat thoracic aorta to noradrenaline

The aim of this study was to investigate the effects of low and high doses of estradiol, and of progesterone on the response to noradrenaline in rat thoracic aorta. Two weeks after bilateral ovariectomy, female rats received a s.c. injection of vehicle (corn oil, 0.1 mL/day), estradiol (10 microg/kg/day or 4 mg/kg/day) and/or progesterone (20 mg/kg/day), for eight days. On the ninth day, the rats were sacrificed and aortic rings, with or without endothelium, were used to generate concentration-response curves to noradrenaline. Aortic rings with intact endothelium from the high-dose (4 mg/kg/day) estradiol group were supersensitive to noradrenaline compared to the vehicle or low-dose (10 microg/kg/day) estradiol groups (pD2 values = 7.86+/-0.09, 7.30+/-0.11 and 7.35+/-0.04, respectively). Endothelium-intact aortic rings from high-estradiol rats were supersensitive to noradrenaline when compared to vehicle-, progesterone- and progesterone + high-estradiol-treated rats (pD2 values = 7.77+/-0.12, 7.21+/-0.13, 6.93+/-0.04 and 7.22+/-0.18, respectively). There were no significant differences among the pD2 values for noradrenaline in aortic rings without endothelium. In conclusion, at high but not low doses, estradiol increased the sensitivity to noradrenaline and this was prevented by progesterone. Both of these effects were endothelium-dependent.     

Changes in the density of peripheral benzodiazepine binding sites in genital organs of the female rat during the oestrous cycle

The affinity and the density of peripheral-type benzodiazepine binding sites (PBzS) in tissues from the genital organs of female rats were studied during the oestrous cycle. When comparing PBzS density on the day of oestrus to PBzS density on the day of pro-oestrus, a significant increase was observed in the ovary (1.9-fold), oviduct (2.4-fold) and uterus (1.7-fold), but not in the kidney. Serum oestradiol also increased to a maximum on the day of pro-oestrus. The ovarian and uterine PBzS density and serum concentrations of oestradiol and progesterone were measured every 8 h between the days of dioestrus and pro-oestrus. Ovarian and uterine PBzS density increased to a maximal value at 01:00 and 09:00 h, respectively, on the day of pro-oestrus. However, a significant increase in PBzS density occurred in the ovary (P less than 0.02) and uterus (P less than 0.001) at 09:00 h on the day of pro-oestrus as compared to 09:00 h on the day of dioestrus. These changes were associated with an increase in serum oestradiol and progesterone concentrations. The affinity of PBzS in all tissues examined remained unaltered during the oestrous cycle. This study demonstrates that changes associated with the oestrous cycle occur in the density of PBzS in various genital organs.     

Potential hepatoprotective activity of ononitol monohydrate isolated from Cassia tora L. on carbon tetrachloride induced hepatotoxicity in wistar rats

Ononitol monohydrate, structurally similar to glycoside was isolated from Cassia tora L. leaves. Fifty Male rats were divided into five groups. Group I served as normal control. Group II, III and IV rats were induced hepatotoxicity by CCl₄ administering single dose of CCl₄ on 8th day only. Group III was treated with ononitol monohydrate (20 mg/kg body weight) and group IV was treated with reference drug silymarin (20 mg/kg body weight) both dissolved in corn oil and administering for 8 days. Ononitol monohydrate with corn oil alone was given for 8 days (group V). At the end of the experimental period all the animals were sacrificed and analyzed for biochemical parameters to assess the effect of ononitol monohydrate treatment in CCl₄ induced hepatotoxicity. In in vivo study, ononitol monohydrate decreased the levels of serum transaminase, lipid peroxidation and TNF-α but increased the levels of antioxidant and hepatic glutathione enzyme activities. Compared with reference drug silymarin ononitol monohydrate possessesed high hepatoprotective activity. Histopathological results also suggested the hepatoprotective activity of ononitol monohydrate with no adverse effect. Hence we conclude that ononitol monohydrate is a potent hepatoprotective agent.     

The effectiveness of steers and heifers treated with oestrogen or testosterone to detect oestrus in cattle

Two experiments were carried out to determine the effectiveness of steers and heifers, treated with oestrogen or testosterone, in the detection of oestrus in cattle.In the first experiment 17 steers castrated at birth and 16 castrated at 6 months of age were randomly allocated to three groups and received an 800 mg subcutaneous implant of testosterone, subcutaneous injections of 10 mg oestradiol benzoate per week for 16 weeks or no hormone (controls). In addition, six heifers were injected subcutaneously with 10 mg oestradiol benzoate per week for 16 weeks while six untreated heifers served as controls. Animals were observed in a standardised libido test 2, 4, 8, 16, 20 and 24 weeks after treatment commenced. The time to first mount and the number of mounts per animal responding in the presence of oestrous heifers were recorded. Both steers and heifers treated with oestradiol benzoate were superior at detection of oestrus in cattle than animals treated with testosterone or those receiving no hormone. Oestrogen-treated animals generally detected heifers in oestrus in less than 3 min after introduction and mounted these animals between 20 and 30 times in one hour. This response was consistent throughout the duration of the experiment. There was no effect of age at castration of steers on development of male behaviour.The second experiment determined the rate and degree of development of male behaviour in steers in response to weekly subcutaneous injections of 0, 2, 4, 8 or 16 mg oestradiol benzoate per 250 kg body weight, 250 mg testosterone or 150 mg dihydrotestosterone for a period of 15 weeks. Steers treated with oestradiol benzoate again proved to be more successful than untreated or testosterone-treated steers at consistently detecting and mounting oestrous heifers. The best response was obtained from steers treated with 8 mg/250 kg body weight per week. The practical application of this work is discussed.     

二月桂酸二丁基锡对大鼠妊娠及对子代毒性作用

目的通过染毒观察二月桂酸二丁基锡（Dibulytin Dilaurate,简称DBTD）对子代胎鼠形态、体重、性别及骨骼发育状的影响。方法按随机分组的原则,将大鼠分为对照组和染毒组,对照组用玉米油,染毒组用DBTD玉米油溶液,浓度分别是2.5 mg/kg体重（1/72 LD50）、10 mg/kg体重（1/18 LD50）和20 mg/kg体重（1/9 LD50）,采用灌胃的方式进行染毒,6 d/周,每天同一时间进行染毒,共计染毒48 d。染毒第五周后,各组大鼠与正常雄性大鼠以1：1的比例合笼,合笼期间不染毒,每只雌鼠查到阴栓为妊娠第0天,继续染毒,于妊娠第18天处死取胎鼠。结果1/18 LD50及1/9LD50剂量组中活胎及胎儿的体重明显下降,1/18 LD50剂量组胎儿的性别开始发生明显的变化（P〈0.05）。结论DBTD染毒对大鼠每胎存活数、胎重、胎儿的形态及性别有影响,有一定的生殖毒性。     

Patterns of protein synthesis in endometrial tissues from ovariectomized rats treated with oestradiol and progesterone

Groups of ovariectomized rats were taken as controls or given hormonal treatment mimicking the successive steps in the sequence of ovarian secretions leading to implantation. Total endometrium or separated epithelium and stroma were incubated in vitro with [35S]methionine. Dissolved proteins were submitted to two-dimensional polyacrylamide gel electrophoresis (pH range 5-7), followed by autoradiography. Priming with oestradiol (2 days) and subsequent treatment with progesterone (3 days) enhanced the synthesis of 12 and 14 polypeptides, respectively, which are specific for each of these treatments. Progesterone also suppressed the production of 10 oestrogen-dependent proteins both in the epithelium and the stroma. When an oestrogen-progesterone-oestrogen treatment was given, synthesis of all but 4 of the progesterone-induced polypeptides in the epithelium was inhibited while 5 of the proteins abolished by progesterone in this tissue compartment reappeared. These results are compatible with a mechanism of implantation acting at the epithelial level by lifting of intrauterine inhibition and stimulation by embryotrophic substances.     

Does exogenous progesterone and oestradiol treatment from the mid-luteal phase induce follicular cysts in goats?

The purpose of the present study was to investigate the effects of exogenous ovarian steroid treatment, which is known to induce follicular cyst experimentally in cows, on ovarian activity in goats. Eleven female Shiba goats with the length of the normal oestrous cycle (approximately 21 days) received subcutaneously either 1 ml of ethanol (control group, n=4) or 4 mg of progesterone and 2mg of oestradiol (treatment group, n=7) daily for 7 days beginning on day 14 of the oestrous cycle (day 0=ovulation). Ultrasonographic images of the ovary and blood samples were collected daily to monitor the ovarian activity. Ovulation was observed before 1 day after the end of treatment in the control group. In the treatment group, no detectable structures of follicles or corpus luteum (static ovarian condition) were found for 6.0+/-1.4 days (mean+/-S.D.) after the end of treatment. Then, detectable follicles appeared and ovulation was observed in all animals of the treatment group. There was no significant difference in the maximum diameter of the ovulatory follicle between the control and treatment group (4.7+/-0.4mm versus 5.1+/-0.7 mm). The large non-ovulatory follicles, which grew more than 10mm in diameter were observed after the static ovarian condition in one goat of the treatment group, whereas no turnover of the cystic follicular structures was found. The length of the inter-ovulatory intervals in the treatment group was significantly longer than that in the control group (38.4+/-7.4 days versus 20.3+/-0.5 days, P<0.05). The present results demonstrated that the exogenous treatment of progesterone and oestradiol, which was adapted from the follicular cyst model in cows, did not induce follicular cysts in goats, suggesting that there is/are different mechanism(s) mediating the occurrence of follicular cysts between cows and goats.     

The effects of 5-bromo-2-thienyl-ethyl-ketone thiosenicarbazone on ovarian cyclicity and ovulation in the rat.

Pseudopregnant and cyclic rats were injected for 5 to 26 days with daily doses of 5 and/or 3 mg of 5-bromo-2-thienyl-ethyl-ketone thiosemicarbazone (70026) starting on Day 0 (the day of oestrus). The vaginal smear cytology, record of ovulation and ability to breed and conceive were compared with the results for corn oil-injected controls. Both doses of 70026 were found to cause a reappearance of pro-oestrous and/or oestrous vaginal smears within 4 to 6 days in the pseudopregnant rats, but ovulations did not occur. The 5-mg dose of 70026 inhibited ovulation and interrupted the oestrous cycle in cyclic rats, even though the daily 3-mg dose seemed to have little effect on ovulation, ovarian cyclicity, breeding or conception. In spite of the absence of an ovulation accompanying the induced pro-oestrous and/or oestrous vaginal smears in the pseudopregnant rats, the pattern of the vaginal smears suggested the occurrence of a 'delayed pseudopregnancy' in most of the pseudopregnant rats treated daily with 3 mg, but in few of those treated with 5 mg, 70026.     

Plasma hormone levels and reproductive behaviour in anoestrous ewes after treatment with progesterone and PMSG

Plasma progesterone and gonadotrophin levels were studied in anoestrous ewes treated during June or July with a subcutaneous progesterone implant and/or an injection of oestradiol or PMSG. Of 32 ewes treated with progesterone during July, 9 showed a gonadotrophin surge after removal of the implant, and 10 ewes showed oestrous behaviour during the following 4 days. Six ewes conceived at this induced oestrous. Progesterone treatment during June was much less effective, with only 2 of 19 treated ewes showing a gonadotrophin surg and oestrous behaviour. Administration of PMSG at the time of implant removal in the June experiment was followed by a gonadotrophin surge and oestrous behaviour in 18 of 19 ewes, and 15 ewes conceived at the induced oestrus. An injection of PMSG, without progesterone pretreatment, stimulated a gonadotrophin surge and ovulation, but did not result in oestrous behaviour. The treatments employed appeared to initiate cyclic ovarian activity in the July experiment, but not in the June experiment.