Studies of the effectiveness of gonadotrophin-releasing hormone, steroids and follicular fluid in modulating ovine gonadotrophin output in vivo and in vitro

Gonadotrophin-releasing hormone (GnRH) readily stimulated LH output by sheep pituitary cells in vitro, and raised plasma LH concentrations in vivo in sheep, in a dose-dependent fashion. However, increases in FSH levels were only marginal by comparison. Dose-dependent decreases in sheep pituitary cell FSH output and in plasma FSH concentrations were caused by sheep follicular fluid and oestradiol-17 beta in vitro, and by bovine follicular fluid and oestradiol benzoate in vivo. In contrast, LH concentrations were only reduced slightly at the higher doses of these reagents. Cumulative suppressive effects of follicular fluid and oestradiol-17 beta (oestradiol benzoate) on FSH levels were observed both in vitro and in vivo. The transient positive feedback effect of oestradiol benzoate on FSH output negated the suppressive effect of bovine follicular fluid on plasma FSH concentrations. Progestagens, androgens and catechol oestrogens also suppressed mean FSH output in vitro, though not as effectively as oestradiol-17 beta. While only 1-5 pg/ml of oestradiol-17 beta was needed to suppress significantly mean FSH output in vitro, greater than 500 pg/ml of the other steroids was required. Seminal plasma inhibin-like peptide failed to suppress mean FSH output by cultured sheep pituitary cells at doses from 1 pg/ml to 500 ng/ml. At higher doses, both FSH and LH output was suppressed and this was accompanied by morphological deterioration of the cells. It is suggested that, to raise plasma FSH concentrations with a view to increasing ovulation rates in sheep, the development of means to reduce the negative feedback effects of steroids, notably oestradiol-17 beta, and inhibin on FSH secretion may be a more appropriate pharmacological strategy than increasing pituitary exposure to GnRH.     

Concentrations of oestradiol-17β and progesterone in the plasma of dairy heifers before and after cloprostenol-induced and natural luteolysis and during early pregnancy

Plasma oestradiol-17β and progesterone levels were measured in seven nulliparous, dairy heifers (British Friesian breed) that were administered cloprostenol (a synthetic analogue of prostaglandin F_2α) between days 8 and 14 of the oestrous cycle and inseminated (AI) 72 and 96 h later, and in seven heifers inseminated (AI) at natural oestrus.In both treated and untreated heifers, the beginning of the progesterone fall and the oestradiol-17β rise associated with luteolysis appeared to be synchronous but, whereas the rate of fall in progesterone level was greater for the treated heifers, that of the oestradiol-17β rise did not differ between treated and untreated heifers. Mean pre-ovulatory peaks of oestradiol-17β were 8 pg/ml and 10 pg/ml for treated and untreated heifers respectively.A post-ovulatory peak of oestradiol-17β in plasma 5–6 days after the pre-ovulatory peak occurred in all heifers whether or not conception had taken place. It is suggested that 7 days after the initiation of oestradiol-17β secretion by the pre-ovulatory follicle, another follicle begins to mature and secrete oestradiol-17β and that the progress of the latter towards full maturation and potential ovulation is stopped by rising progesterone levels from the corpus luteum; as a result in normal, non-pregnant cattle an interval of about 21 days elapses before another ovulation (of another follicle) takes place. In the event of premature luteolysis (in the present study induced between the 8th and 14th day) there is no evidence that the timing of this luteolysis influences the time taken for a follicle to enter the final stages of pre-ovulatory maturation, when increasing amounts of oestradiol-17β are secreted. Thus the interval between ovulations may not be less than 7 days but, depending on corpus luteum survival, may vary between 7 and 21 days.In one heifer after natural luteolysis a normal plasma oestradiol-17β peak followed but this was not associated with ovulation and corpus luteum formation. The second oestradiol-17β peak 6 days after the first, however, evidently assumed the ovulatory role; presumably the secreting follicle concerned, not being subject to inhibition by progesterone rising to luteal levels, matured fully and ovulated. Thus the second, normally post-ovulatory, oestradiol-17β peak in cattle can, in the event of failure of ovulation at the normal time, itself assume the ovulatory function, the oestrous cycle length then being about 28 days.     

Oviductal isthmic motility patterns as monitored by polyview in unrestrained sows around ovulation

A method for monitoring oviductal isthmic motility in sows incorporating a computer programme (Polyview) was developed. This method was found to be reliable and easy for recording and analysing data. Isthmic motility patterns were monitored from 11 h prior to and up to 36 h after ovulation in 13 unrestrained multiparous sows during their second oestrus after weaning. The amplitudes and frequencies of phasic pressure fluctuations in relation to the hormonal profiles were also calculated. The isthmic motility patterns were regular before ovulation changing to wave patterns during the peri-ovulatory period and eventually to irregular patterns after ovulation. The amplitudes and frequencies of phasic pressure fluctuations were significantly higher (p<0.05) prior to and soon after ovulation than afterwards. Plasma oestradiol-17beta levels significantly (p<0.05) decreased before ovulation while plasma progesterone levels increased significantly (p<0.05) after ovulation. Despite a significant decrease in the plasma levels of oestradiol-17beta prior to ovulation, the amplitudes and frequencies of phasic pressure fluctuations remained high until shortly after ovulation. This could have been due to the endogenous levels of oestradiol-17beta bound to the nuclear oestradiol-17beta receptors that might still have been present in the isthmus. Conversely, the irregular isthmic motility patterns, the decline in the frequencies of phasic pressure fluctuations and amplitudes seen after ovulation may have been due to the rising plasma levels of progesterone. The amplitudes and frequencies of phasic pressure fluctuations were highest at the time when oestradiol-17beta levels were highest and when progesterone levels were low. It can be concluded that the changes in the isthmic motility patterns, amplitudes and frequencies of phasic pressure fluctuations in relation to the changes in the plasma levels of oestradiol-17beta and progesterone seen in the present study prior to and after ovulation indicate a possible role of the oviduct in regulating gamete transport.     

Effect of Chlorpromazine on the Binding of Oestradiol-17β by Human Uterine Cytosol

Abstract

Chlorpromazine increases the binding of oestradiol-17β by human uterine cytosol in vitro. This effect is due to an increase in the number of receptor sites, and the dissociation constant for oestradiol-17β is unaffected by chlorpromazine.     

Attainment of puberty in female pigs: Clinical appearance and patterns of progesterone,oestradiol-17β and LH

The object of the study was to investigate the clinical and endocrine patterns of progesterone, oestradiol-17β and LH during the peripubertal period in female pigs. Crossbred gilts were penned in groups at an age of 10–12 weeks and boars were kept in adjacent pens during the entire experimental period. Daily oestrous checks started at 4.5 months of age and the gilts were slaughtered after their third heat. At the age of 4.5–5 months a permanent catheter was inserted in the cephalic vein and blood samples were collected from the gilts once daily until either the first or second oestrus. In three gilts hourly blood samples were taken during their first and second oestrus, beginning at early pro-oestrus.The gilts showed their first oestrus at the average age of 183 days. No corpora lutea from earlier ovulations were observed in gilts laparoscoped after their first detected oestrus. During the 30-day period before first oestrus the mean daily progesterone levels varied between 32 and 329 pmol/l. The average levels of oestradiol-17β varied between 15.6 and 30.8 pmol/l. There was no tendency for the oestradiol-17β level to rise before onset of first pro-oestrus. The average levels of LH varied between 0.15 and 0.94 μg/l. The statistical analyses revealed no significant relationship between the level of the hormones studied and onset of first oestrus. The mean progesterone levels during the first and second oestrous cycles were almost identical, however. Oestradiol-17β increased gradually during pro-oestrus, reaching maximum levels before onset of oestrus and thereafter decreasing sharply to values around 30 pmol/l. The oestradiol-17β levels were higher at the second than at the first pro-oestrous period. The concentrations of plasma LH rose sharply with declining plasma levels of oestradiol-17β. The duration of elevated plasma LH levels (> 1 μg/l) was, on average, 26 h and the LH levels were higher during the first oestrus than during the second oestrus. The first rise in progesterone was observed 11–29 h after the LH levels had decreased to concentrations below 1 μg/l.     

Ovarian steroid hormone involvement in endogenous opioid modulation of LH secretion in mature ewes during the breeding and non-breeding seasons

The opioid antagonist WIN-44441-3 (WIN-3, Sterling-Winthrop) caused significant increases in LH secretion in ovariectomized ewes treated with progesterone but not in ovariectomized animals treated with oestradiol-17 beta. In the non-breeding season, plasma LH concentrations in ovariectomized ewes without steroid therapy, given oestradiol-17 beta or oestradiol-17 beta and progesterone together were not affected by treatment with WIN-3 on Day 6 after ovariectomy (there was a significant increase in LH as a result of WIN-3 treatment 13 days after ovariectomy in sheep given no steroid therapy). However, WIN-3 treatment of ovariectomized sheep given progesterone resulted in a significant increase in plasma LH. WIN-3 was ineffective when given to intact ewes treated with progesterone during the non-breeding season. With ovariectomized sheep during the breeding season there was again no response to WIN-3 at 6 days after ovariectomy in sheep given oestradiol-17 beta, but significant LH elevations in animals given no steroid, those given progesterone and those given progesterone + oestradiol-17 beta. The lack of an LH response to WIN-3 in ovariectomized sheep treated with oestradiol-17 beta did not result from a reduced pituitary response to GnRH since such animals responded normally to exogenous GnRH treatment. Overall, these results are consistent with the idea that, irrespective of the time of year, progesterone exerts negative feedback upon LH release at least in part through an opioidergic mechanism, whereas oestradiol-17 beta exerts negative feedback through steps unlikely to involve opioids. Progesterone can override the effect of oestradiol-17 beta during the breeding season only. Further, there appears to be a steroid-independent opioid involvement in LH suppression, operating at both times of year.     

Plasma levels of oestradiol-17 beta in the pre-puberal heifer treated to induce superovulation

The plasma concentrations of oestradiol-17β have been measured by radioimmunoassay in pre-puberal calves following treatments used to induce superovulation (PMSG/HCG and PMSG/FGA/HCG). Before treatment, in almost all animals, the concentrations of oestradiol-17β were different from zero (2 to 8 pg/ml). The highest concentrations were measured around 130 h. after the beginning of treatment, before ovulation (150 to 2050 pg/ml). The curves showing the changes in hormonal levels have the same form as those of follicular growth measured using morphological criteria. The two hormonal treatments resulted in similar oestradiol-17β concentrations.     

Bovine Colostrum Levels of Oestrone and Oestradiols

The levels of free and conjugated oestrone, oestradiol-17β and oestradiol-17α were estimated in bovine colostrum of the 1st, 2nd and 3rd drawing. The values obtained of free oestrone and oestradiol-17β were generally below the lowest value significantly (P = 0.01) different from zero (4.5–5.0 µg per 1) in the method applied. The values of conjugated oestrone and oestradiol-17β in the first drawing exceeded the lowest value significantly different from zero (1.5–2.0 µg per 1) by factors of 2–4 and averaged 6.1 and 3.7 µg per 1 respectively in the five cows examined. The levels of conjugated oestrone and oestradiol-17β in the 2nd and the 3rd drawing were apparently lower than in the 1st drawing. As compared with the values obtained of free and conjugated oestrone and oestradiol-17β, the corresponding values of oestradiol-17α were generally much smaller, in none of the samples exceeding 1 µg per 1. In some samples oestradiol-17α could not be detected. The results are discussed in relation to previous bioassays of colostrum oestrogens.     

Luteinizing hormone and oestradiol-17β in blood plasma and milk during the oestrous cycle and early pregnancy in Murrah buffaloes

Immunoreactive luteinizing hormone and oestradiol-17β were measured by radioimmunoassay in 28 Murrah buffaloes. The concentration peaked sharply in blood plasma (plasma) coincident with the onset of oestrus (range 0 to +6 h), whereas the oestradiol-17β concentration increased before the onset of oestrus (range ?8 to ?17 h). There were erratic fluctuations in the LH concentration in milk which did not correlate with the concentration in the plasma. However, the basal concentration of LH in milk was significantly higher (P < 0.01) than in plasma. The oestradiol-17β concentration in milk mimicked that in plasma and was significantly higher (P < 0.001) than in plasma. There was no significant difference (P > 0.05) of these hormones in primiparous and multiparous animals.     

Competitive protein-binding assay of estrone, estradiol-17 or estradiol-17 in human or ruminant plasma

A procedure for the assay of estrone, estradiol-17β or estradiol-17α in plasma is described. The technique also appears applicable to the assay of estriol in plasma. The procedure uses a semi-automatic extraction of plasma, rapid micro-alumina column chromatography and competitive binding of the estrogens to stable proteins of sheep uterine cytosol. The use of alumina column chromatography results in consistently low blanks. The assay has been evaluated for the measurement of estradiol-17β and estrone in human and sheep plasma, and for estradiol-17α and estrone in goat plasma. The change in binding affinity of estradiol-17α relative to estradiol-17β when incubated in sheep uterine cytosol at two different temperatures (25°C and 4°C), makes it possible to differentiate the two epimers of estradiol. Measurement of estradiol-17β down to 10 pg and of estrone and estradiol-17α to 25 pg are maintained in routine analyses. The specificity of the procedure was thoroughly checked by various methods, including comparison with spectrophotofluorimetric analysis.     

Plasma Levels of Progesterone and Oestradiol-17 β in Reindeer (Rangifer Tarandus Tarandus) During Pregnancy

The plasma concentrations of progesterone and oestradiol-17p during pregnancy and the first 20 days after parturition were estimated in reindeer. The concentration of progesterone in the period 75–25 days prior to parturition was significantly higher than in the period 200– 75 days prior to parturition (P < 0.001). During the last 25 days before parturition the concentration decreased significantly. The concentration of oestradiol-17β was in most cases below 70 pg/ml until 50 days prior to parturition. During the last 25 days of pregnancy there was a significant increase in oestradiol-17β and the ratio progesterone/ oestradiol-17β was markedly lower than in the period 75–25 days before calving.     

Effect of Quinoline-Type Antimalarial Drugs on the Binding of Oestradiol-17β and Progesterone by Rabbit and Human Uterine Cytosols

Abstract

Rabbit and human uterine cytosol, prepared and tested in phosphate buffer, bound less oestradiol-17β or progesterone than cytosol from the same source prepared and tested in Tris-HCl buffer. Dissociation constants were the same in both buffer systems, and the difference in binding was due to a difference in the number of binding sites. Three quinoline-type antimalarial drugs, chloroquine, quinine and mefloquine, and the quinoline derivative, 4-(4'-hydroxy-l'-methylbutylamino)-7-chloroquinoline, increased the steroid binding capacity of phosphate-buffered cytosol to that of Tris-buffered cytosol, the optimal concentration of quinoline derivative being 1.4–1.6 mM. Tris (50 mM) increased the binding capacity of phosphate-buffered cytosol to that of Tris-buffered cytosol. The effects of Tris and quinoline derivatives were not additive. By gel chromatography and sucrose density gradient centrifugation it was shown that the molecular size and sedimentation behaviour of the oestradiol and progesterone receptors were not affected by the quinoline derivatives. Two types of binding site are proposed, one requiring the presence of low molecular weight, basic compounds. The uterine levels of chloroquine attained by normal pharmacological doses of the drug are potentially capable of influencing the binding of oestradiol-17β and progesterone in the uterine cytosol.     

Progestagen,androgen and oestrogen levels in plasma and ovarian follicular fluid during the oestrous cycle of the mare

The pattern of steroid hormone concentrations in the blood plasma of five mares was determined throughout eight oestrous cycles by radioimmunoassay. In three other mares the steroid hormone concentrations in the follicular fluid of 16 isolated follicles (⪖ 1 cm diameter) from both ovaries were analyzed on the first and third day of behavioural oestrus.The plasma levels of pregnenolone and progesterone as well as their 17α-hydroxylated metabolites showed similar ranges of concentration throughout the oestrous cycle. Luteolysis occurred 6 days prior to ovulation and was accompanied by a drop of all progestagens. Throughout the oestrous period (5 days prior to and including the day of ovulation) mean plasma concentrations of progestagens were <0.5 ng/ml and increased significantly one day after ovulation. Maximum plateau values were reached on day 6 after ovulation. A distinct (but not statistically significant) rise of androstenedione and testosterone plasma levels occurred during oestrus whereas dehydroepiandrosterone values increased significantly 6 days prior to ovulation and reached a maximum mean value of 1.14 ng/ml one day before ovulation. Levels then declined significantly on the day of ovulation. Oestrone and oestradiol-17β plasma concentrations increased significantly 4 and 3 days prior to the day of ovulation, respectively, and both remained elevated until one day before ovulation.A significant positive correlation could be detected between increasing follicle diameters and androstenedione as well as oestradiol-17β concentrations in the follicular fluid, whereas pregnenolone values showed a negative correlation with follicular diameter. Oestradiol-17β could be determined in 9 of the 16 follicular fluid samples. In 8 of these 9, oestradiol-17β predominated over all other steroid hormones.In view of the low concentrations of dehydroepiandrosterone detected in the follicular fluid, it is suggested that the increase in peripheral plasma values during oestrus is caused by an extra-follicular source(s).     

Effect of intrauterine application of oestradiol-17 beta and prostaglandin E-2 on the porcine oestrous cycle and uterine endocrinology.

Silastic beads were inserted into the uterine lumen on Day 10 after oestrus. Gilts received beads containing oestradiol-17 beta only, oestradiol benzoate, or oestradiol-17 beta+prostaglandin (PG) E-2. Oestrous cycles were slightly longer in treated than in untreated pigs (20.2 +/- 0.4 days), and durations were 22.6 +/- 1.3, 26.2 +/- 1.7 and 23.2 +/- 1.8 days for oestradiol-17 beta, oestradiol benzoate and oestradiol-17 beta+PGE-2 treatments, respectively (P greater than 0.05). Thus, PGE-2 and an oestrogen such as oestradiol benzoate that persist for a longer period cannot prolong the cycle more than oestradiol-17 beta alone. Additional cyclic gilts underwent similar treatments with beads containing oestradiol-17 beta, oestradiol-17 beta+PGE-2 or cholesterol, and cannulation of one utero-ovarian vein on Day 10. Blood samples were collected from the catheter every 15 min from 08:00 until 11:00 h and from 20:00 until 23:00 h for 5 consecutive days starting the day after surgery and peripheral plasma samples were also collected daily. On Day 16, beads containing oestradiol-17 beta were surrounded by endometrial folds whereas cholesterol beads were free. Concentrations of plasma progesterone did not vary significantly from Days 11 to 16 in gilts treated with oestradiol-17 beta or oestradiol-17 beta+PGE-2, but decreased in cholesterol-treated gilts. Concentrations of plasma oestrone and oestradiol-17 beta were more than ten times higher in gilts treated with oestradiol-17 beta or oestradiol-17 beta+PGE-2 than in cholesterol-treated gilts on the day after bead insertion, but decreased rapidly to values comparable to those in cholesterol-treated gilts by Day 14. In contrast, concentrations of oestrone sulphate remained high until Day 16. Concentrations of PGE-2 in the utero-ovarian vein plasma did not differ (P greater than 0.05) between treatments but those of PGF-2 alpha were higher (P less than 0.004) in gilts treated with cholesterol than in those treated with oestradiol-17 beta or oestradiol-17 beta+PGE-2. It is postulated that insufficient oestradiol-17 beta is released by the beads toward the end of a 'recognition period' to prolong the cycle for more than 3-6 days.     

The ovarian and hormonal response of the ewe to stimulation by the ram early in the breeding season

The introduction of Dorset rams to Romney ewes at the beginning of the breeding season (February 14 to March 1) stimulated 39% to 70% of the non-cycling ewes to ovulate. Most of the ewes that ovulated did so within 65 to 72 hours of ram introduction. The ovulations were preceded by LH peaks, the mean onset of which was 35.0±4.8 (SE) hours after ram introduction. The mean oestradiol-17β concentration per ewe ranged from 0.3 to 14.9 pg/ml plasma and there were large fluctuations among the samples collected every 3 hours. All ewes, irrespective of treatment, had similar mean concentrations of oestradiol-17β and ovarian follicular activity, and there were no changes in oestradiol-17β concentration that could be attributed to the presence of the rams.     

Influence of age,weaning, season and body weight on the levels of progesterone,oestradiol-17β and luteinizing hormone in growing buffalo heifers (Bubalus bubalis)

The influence of age, weaning, season of the year and body weight on the peripheral levels of progesterone, oestradiol-17β and luteinizing hormone (LH) were studied during neonatal, perinatal and peripubertal periods in buffalo heifers. The buffalo heifers exhibited oestrus only after 30 months of age and had higher levels of LH and oestradiol-17β and a lower level of progesterone on the day of oestrus. The progesterone concentration was affected significantly (P < 0.01) by different seasons, by weaning (P < 0.05) and varied between pubertal and neonatal periods (P < 0.01), whereas the oestradiol-17β level was affected significantly (P < 0.01) by weaning and varied at different seasons and with body weight. However, the LH concentration was greater during the neonatal period than the pre- and peripubertal periods and changed significantly (P < 0.01) between groups of ages and body weights. The results suggest that increases in the levels of oestradiol-17β and progesterone after 30 months of age are probably indicative of the onset of puberty in buffalo heifers. However, a further increase in oestradiol-17β, LH, and a decrease in progesterone are essential for oestrus and cyclicity to be exhibited in buffalo heifers.     

Inhibitory effect of progesterone on cell death of mouse uterine epithelium

The protective effect of progesterone against cell death of mouse uterine epithelium was evaluated by examining the retention of 5'-[125I]iodo-2'-deoxyuridine [( 125I]IdUrd) incorporated into the whole uterus and the apoptotic index (percentage of apoptotic cells in total cells), which is a good index of physiological cell death. Castrated adult female mice were given a daily injection of oestradiol-17 beta for 3 days, and then an injection of [125I]IdUrd. They were then divided into 4 groups, which received a daily injection of vehicle only, oestradiol-17 beta (E), progesterone (P), or both oestradiol-17 beta and progesterone (EP), and were killed at intervals during these treatments for determination of 125I radioactivity retained in the whole uterus. On treatment with vehicle only, the 125I radioactivity retained in the uterus decreased rapidly, but treatment with E, P or EP reduced the loss of 125I radioactivity significantly. Progesterone did not antagonize the effect of oestradiol-17 beta on the 125I radioactivity retained in the uterus. The apoptotic index of uterine cells was examined by a similar experimental protocol, but without injection of [125I]IdUrd. In the group treated with vehicle only, the apoptotic indices of both luminal and glandular epithelia increased markedly, but the injection of E, P or EP suppressed these increases significantly. Progesterone did not antagonize the effect of oestradiol-17 beta on the apoptotic index. The apoptotic index of stroma was not affected by the injection of E, P or EP. On the other hand, progesterone completely inhibited the increase in the mitotic index of uterine epithelia induced by oestradiol-17 beta. These results show that progesterone alone or in combination with oestrogen reduced cell death in mouse uterine epithelium and that the effects of oestrogen and progesterone on uterine cell death were independent of their actions on cell division.     

Effects of oxytocin,vasopressin and vasotocin and their agonists on steroid secretion by bovine granulosa cells

The effects of oxytocin and vasopressin and their agonists on the secretion of progesterone and oestradiol-17β by bovine luteinised granulosa cells cultured in a serum-supplemented medium were analysed. The effects of oxytocin (OT), its long-acting agonist 2-0-methyl-tyrosin (deamino-karba)-oxytocin (DK-OT), arginine-8-vasopressin (AVP), 1-desamino-arginine-8-vasopressin (D-AVP, a vasopressin analogue with high antidiuretic and without vasopressor properties) and arginine-8-vasotocin (AVT) were investigated. It was found that OT and DK-OT had a stimulatory effect on progesterone release, while AVP, D-AVP and AVT had an inhibitory effect. All peptide hormones investigated significantly increased oestradiol-17β secretion. The results suggest the involvement of nonapeptide hormones of both oxytocin and vasopressin groups in the regulation of steroidogenesis by granulosa cells from bovine ovarian follicles.     

Influence of SLA haplotype on ovulation rate and litter size in miniature pigs

Systemic blood was collected from and surgery performed on sows of 3 strains of miniature swine bred for specific SLA (swine MHC) haplotypes (a, c and d) from Day 2 to Day 6 after mating (first day of mating = Day 0). Ovulation rate was determined by counting corpora lutea and embryos were flushed from the uterus. Progesterone, oestradiol-17 beta and oestrone were quantitated in blood plasma and uterine flushings by RIA. SLAd/d females had a higher ovulation rate than SLAa/a or SLAc/c females (11.50 +/- 0.87 vs 9.11 +/- 0.68 and 8.17 +/- 0.83, respectively; P less than 0.01). Oestrone was higher than oestradiol-17 beta in systemic plasma (56.5 +/- 6.4 vs 33.0 +/- 4.7 pg/ml, P less than 0.01) while oestradiol-17 beta was higher than oestrone in uterine flushings (19.8 +/- 1.4 vs 14.9 +/- 1.5 pg/horn, P less than 0.10). Systemic progesterone concentration was correlated with day after mating (r = 0.93, P less than 0.01). There was no effect of haplotype on any of the hormone concentrations measured. Litter size was analysed from 99 matings amongst SLAa/a, SLAa/c, SLAa/d, SLAd/c and SLAd/d sires and dams. Litter size from -/d and d/d sows or from d/d boars were larger (P less than 0.05) than for all other matings. Although ovulation rate was higher in SLAd/d sows, the significant effect of sire SLA genotype on litter size suggests an additional effect of the d haplotype on embryonic survival.     

Effects of ACTH on the uterine weight response to HCG in mice.

The effects of ACTH and dexamethasone on the uterine weight of immature mice treated with HCG or oestradiol-17 beta were studied. The animals were treated daily for 3 days and wet and dry uterine weights were measured on the 4th day. Low doses of ACTH (1-25 mug/day) raised the sensitivity of the uterine weight response to threshold doses of HCG (0-05 to 0-1 i.u.). By increasing the doses of ACTH or HCG, the stimulation gradually turned into inhibition. By itself, ACTH was ineffective and it had no influence on the increase in uterine weight induced by oestradiol-17 beta. Dexamethasone failed to stimulate the effect of HCG.