Effect of progesterone and oestradiol benzoate on oestrous behaviour and secretion of luteinizing hormone in ovariectomized fallow deer (Dama dama).

Eighteen ovariectomized fallow deer does and two adult bucks were used to investigate the effect of exogenous progesterone and oestradiol benzoate on oestrous behaviour and secretion of luteinizing hormone (LH). In Expts 1 and 2, conducted during the breeding season (April-September), does were treated with intravaginal Controlled Internal Drug Release (CIDR) devices (0.3 g progesterone per device) for 12 days and differing doses of oestradiol benzoate administered 24 h after removal of the CIDR device. The dose had a significant effect on the proportion of does that exhibited oestrus within the breeding season (P less than 0.001), the incidence of oestrus being 100% with 1.0, 0.1 and 0.05 mg, 42% for 0.01 mg and 0% for 0.002 mg oestradiol benzoate. There was a significant log-linear effect of dose on the log duration of oestrus, which was 6-20, 2-14, 2-12 and 2 h after treatment with 1, 0.1, 0.05 and 0.01 mg of oestradiol benzoate, respectively. Dose had a significant effect on the peak plasma LH concentration (P less than 0.01), mean (+/- s.e.m.) surge peaks of 27.7 +/- 2.3, 25.9 +/- 1.8 and 18.6 +/- 3.4 ng/ml being observed following treatment with 1, 0.1 and 0.01 mg oestradiol benzoate respectively. In Expt 3, also conducted during the breeding season, progesterone treatment (0 vs. 6-12 days) before the administration of 0.05 mg oestradiol benzoate had a significant effect on the incidence of oestrus (0/6 vs. 10/12, P less than 0.05), but not on LH secretion. The duration of progesterone treatment (6 vs. 12 days) had no effect on oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of prolactin on conceptus survival and uterine secretory activity in pigs

Hypoprolactinaemia was induced by bromocriptine (CB154; 100 mg/day) which decreased circulating prolactin by 40% (P less than 0.06), but did not affect conceptus survival at Day 25 when administered on Days 10-16 when compared to saline:ethanol-treated control gilts. Bromocriptine or vehicle was administered to cyclic gilts on Days 10-11, oestradiol valerate was injected on Day 11 and uterine flushings were collected on Day 12. Total recoverable protein and uteroferrin in uterine flushings were not affected by treatment. However, leucine aminopeptidase activity (P less than 0.02) and total recoverable Ca2+, Na+, K+ and Cl- (P less than 0.05) were decreased in uterine flushings of gilts that received bromocriptine, suggesting that hypoprolactinaemia decreased general secretory activity of the endometrial epithelium and modulated ionic changes, respectively, in the uterine environment of pigs. Subcutaneous administration of pig prolactin (1 mg/12 h) increased (P less than 0.001) serum prolactin 4.5-fold. The interaction between hyperprolactinaemia and progesterone, without oestrogen, on components of uterine flushings were determined using gilts that received progesterone (200 mg/day) and prolactin or saline on Days 4-14 after ovariectomy on Day 4. On Day 15, there were no differences (P greater than 0.05) in any of the uterine secretory components measured. Hyperprolactinaemia (1 mg pig prolactin on Days 6-11) enhanced overall uterine secretory response on Day 12 to oestradiol (5 mg) administered on Day 11 compared to gilts that received 1 ml saline on Days 6-11 of the oestrous cycle. Total recoverable protein and leucine aminopeptidase activity were greater (P less than 0.05) for oestradiol-treated gilts, but effects of prolactin were not significant. Total recoverable glucose (P less than 0.01), PGF-2 alpha (P less than 0.02), uteroferrin (P less than 0.01) and specific activity of uteroferrin (P less than 0.001) were increased by prolactin and oestradiol, but not oestradiol alone. Calcium (P less than 0.05), chloride (P less than 0.05) and potassium (P less than 0.01) were increased in response to oestradiol. These results indicate an interaction between oestradiol and prolactin, but not progesterone and prolactin, which enhances secretion of some products of the pig uterine endometrium.     

Prolactin and LH release in response to LH-RH and TRH in ewes during dioestrus, pregnancy and post partum

With advancing pregnancy in the ewe there was a marked decline in plasma LH concentrations and pituitary LH-RH responsiveness (integrated LH release) and a marked increase in plasma prolactin values and pituitary TRH responsiveness (integrated prolactin release). In lactating ewes plasma LH levels and pituitary LH-RH responsiveness had returned to values found in the luteal phase of the normal cycle by 21 days post partum, whereas at 42 days post partum prolactin levels were still high. No interaction between TRH and LH-RH on prolactin and LH release in dioestrous ewes was detected. In non-pregnant ewes plasma prolactin levels were significantly higher in June than in January but TRH responsiveness was similar. It is concluded that, in sheep, pituitary LH secretion recovers more rapidly from the chronic negative feedback effect of oestrogens and progesterone in pregnancy than prolactin secretion recovers from the chronic positive feedback effects of oestrogens. This finding may be a contributory factor in the resistance to resumption of breeding activity.     

Critical progesterone requirement for maintenance of pregnancy in ovariectomized rats

The minimum progesterone concentration required to maintain the pregnancy was studied by varying doses of progesterone given subcutaneously to rats ovariectomized on Day 8 of pregnancy. Injecting 3 mg progesterone plus 200 ng oestradiol benzoate daily provided serum progesterone values between 25.4 +/- 7.0 and 35.2 +/- 6.2 ng/ml throughout Days 10-19 which were significantly lower than normal levels (P less than 0.05), but resulted in 93.6% of fetal survival on Day 19 which was not significantly different from 93.3% in the control group. Injecting 2 mg progesterone plus 200 ng oestradiol benzoate daily gave progesterone values between 13.2 +/- 4.6 and 19.0 +/- 6.2 ng/ml and could not maintain fetal viability to Day 19 (14.2%, P less than 0.05 compared with control group). Critical times to supplement progesterone in rats ovariectomized on Day 8 or Day 15 were studied by varying the time of progesterone implantation after ovariectomy. Progesterone implants were administered 8, 12 and 24 h after ovariectomy on Day 8 and 24, 36 and 48 h after ovariectomy on Day 15. On Day 8, progesterone replacement could be delayed to 8 h but not 12 h, while on Day 15, progesterone replacement could be delayed up to 36 h but not 48 h after ovariectomy without affecting fetal survival.     

Comparison of mammalian luteinizing hormone releasing hormone (LH-RH), and of an analog (ICI 118630), on luteinizing hormone and ovarian steroid (progesterone, oestradiol) secretions in laying hens. (Gallus domesticus)

This experiment was conducted to compare the luteinizing hormone (LH), progesterone (P4) and oestradiol (E2) release in response to injections of various doses of synthetic mammalian luteinizing hormone-releasing hormone (LH-RH) and of an LH-RH agonist, ICI 118630, administered to laying hens 4 to 9 hours after a mid-sequence ovulation. Plasma LH increased significantly within 10 minutes of injection of either compound whereas any increases in plasma steroid concentrations were discerned later, at approximately minutes post-injection. No dose-response relationship was found for either compound with respect to LH release, but ICI 118630 appeared more potent than LH-RH. This analog also produced a greater mean incremental rise in plasma progesterone, but not oestradiol, than LH-RH, and this was found in animals injected at a time when the largest ovarian follicle was not mature. These result suggest that ICI 118630 is a more potent releasing hormone in the hen at the level of the pituitary, and that it may have a stimulating effect on ovarian progesterone secretion.     

Effect of endogenous and exogenous progesterone on the oestradiol-induced LH surge in dairy cows

Four cows released an LH surge after 1.0 mg oestradiol benzoate administered i.m. during the post-partum anoestrous period with continuing low plasma progesterone. A similar response occurred in the early follicular phase when plasma progesterone concentration at the time of injection was less than 0.5 ng/ml. Cows treated with a progesterone-releasing intravaginal device (PRID) for 8 days were injected with cloprostenol on the 5th day to remove any endogenous source of progesterone. Oestradiol was injected on the 7th day when the plasma progesterone concentration from the PRID was between 0.7 and 1.5 ng/ml. No LH surge occurred. Similarly, oestradiol benzoate injected in the luteal phase of 3 cows (0.9-2.1 ng progesterone/ml plasma) did not provoke an LH surge. An oestradiol challenge given to 3 cows 6 days after ovariectomy induced a normal LH surge in each cow. However, when oestradiol treatment was repeated on the 7th day of PRID treatment, none released LH. It is concluded that ovaries are not necessary for progesterone to inhibit the release of LH, and cows with plasma progesterone concentrations greater than 0.5 ng/ml, whether endogenous or exogenous, did not release LH in response to oestradiol.     

Effects of progesterone and oestradiol-17 beta on oxytocin-induced release of prostaglandin F-2 alpha in heifers

Seven bilaterally ovariectomized heifers were used in 4 experiments and received: (1) saline injections, as control; (2) one injection of oestradiol (3 mg; i.v.); (3) two i.v. injections of oxytocin (100 i.u.) 6 h apart; or (4) one oestradiol injection 30 min after the first oxytocin injection and a second oxytocin injection 6 h later. All experiments were performed without progesterone and then after 7, 14 and 21 days of progesterone treatment. Frequent blood samples were taken for 1 h before and 7 h after the first injection of oxytocin or oestradiol for the measurement of 13,14-dihydro-15-keto-PGF-2 alpha (PGFM) by radioimmunoassay. After 7, 14 and 21 days of progesterone priming, oestradiol caused a significant increase (P less than 0.001) in plasma PGFM after 6 h but not before. After 7, 14 and 21 days of progesterone, there was a significant increase (P less than 0.005) in PGFM after the first oxytocin injection and a similar increase following the second. The oxytocin-induced increase in PGFM after 14 and 21 days of progesterone was significantly higher (P less than 0.001) 6 h after oestradiol injection than before the oestradiol injection. There was no significant effect of oestradiol on the response to oxytocin in animals that received no progesterone or in those animals that received progesterone for only 7 days. These results show that, under the influence of progesterone, oestradiol enhances the oxytocin-induced release of PGF-2 alpha, and suggest a possible synergistic action of these hormones for the induction of luteolysis in heifers.     

Effects of ovine conceptus secretory proteins and progesterone on oxytocin-stimulated endometrial production of prostaglandin and turnover of inositol phosphate in ovariectomized ewes.

This study examined the effects of progesterone and intrauterine injection of ovine conceptus secretory proteins (oCSP) on endometrial responsiveness to oxytocin. Twelve ewes were ovariectomized on day 4 of the cycle (oestrus = day 0) and assigned in a 2 x 2 factorial arrangement, to receive either 1.5 mg ovine serum proteins (SP) or oCSP containing 25 micrograms ovine trophoblast protein 1 (oTP-1) (by radioimmunoassay) in 1.5 mg total protein into each uterine horn, via catheters, twice a day on days 11, 12, 13 and 14. Ewes received 200 mg progesterone per day (i.m.) from day 4 to day 10 or 15. Oxytocin-induced prostaglandin F2 alpha was measured as 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) on days 11, 12, 13 and 14 in plasma from three integrated, 10 min (10 ml) blood samples (0-10, 10-20, 20-30 min) obtained after intravenous injection of 20 iu oxytocin, and in a pre-oxytocin (-10 to 0 min) sample collected via an indwelling jugular catheter. The pre-oxytocin samples were also assayed for progesterone. Oxytocin-induced turnover of inositol phosphate was determined in endometrium on day 15 after hysterectomy. In ewes receiving progesterone to day 10, plasma progesterone decreased from about 12 to 2 ng ml-1 (SEM +/- 2.6) during the treatment period (days 11-14), but remained high (12-20 +/- 2.6 ng ml-1) in ewes that received progesterone to day 15. Intrauterine injection of oCSP resulted in high basal concentrations of PGFM on days 12 and 13 compared with SP-treated ewes (P less than 0.01). Treatments with progesterone did not affect basal PGFM concentrations. Treatment with oCSP abolished oxytocin-induced endometrial secretion of prostaglandin only if progesterone was maintained to day 15 (P less than 0.01); in ewes receiving such treatment, oCSP inhibited (P less than 0.01), but SP did not inhibit, oxytocin-induced endometrial turnover of inositol phosphate (P less than 0.06), which was greater in ewes treated with progesterone to day 10 than in those treated to day 15 (P less than 0.05). Ewes that responded to oxytocin with increased PGFM exhibited increased oxytocin-stimulated turnover of inositol phosphate on day 15. These results indicate that the antiluteolytic action oTP-1 exerts on the endometrium requires progesterone and that this mechanism involves inhibition of oxytocin-stimulated turnover of inositol phosphate.     

Maintenance of unimplanted fertilized ova in sprayed rats. IV. Effects of duration of ovarian hormone deprivation and progesterone therapy prior to the deprivation

Studies were carried out in the spayed-rat delayed-implantation model to determine whether progesterone treatment prior to an ovarian hormone deprivation during the pre-implantation period would influence the incidence of subsequent delayed ovo-implantation induced with progesterone plus estrone. Implantation was rarely induced with 4 mg progesterone plus 1 microgram estrone/day after 5 to 11 days of ovarian hormone deprivation in rats that were spayed on Day 3, if progesterone treatment were not given before ovarian hormone deprivation. In contrast to this, implantation was fairly consistently induced with 4 mg progesterone plus 1 microgram estrone/day after 3, 5, 7, or 11 days of ovarian hormone deprivation in rats that were spayed on Day 3 and received 4 mg progesterone/day before the deprivation period (i.e., on Days 2 through 3, 2 through 6, or 2 through 8). The post-implantation viability of the embryos of the dams undergoing the longer periods of ovarian hormone deprivation, however, was reduced.     

The feedback effects of sex steroid hormones on pituitary gonadotropin release in Turner's syndrome and Klinefelter's syndrome.

The present study was designed to elucidate the feedback relationship between the release of pituitary gonadotropins and sex steroid hormones in Turner's syndrome and Klinefelter's syndrome. LH-RH stimulation test was employed to evaluate the effects of sex steroids on the release of gonadotropins. The release of gonadotropins in response to LH-RH as well as in baseline level was suppressed after the treatment with estrogen (mestranol 0.08 mg/day) for 10 days, followed by the treatment of the same period with estrogen (mestranol 0.08 mg/day) and progesterone (chlormadinone acetate 2.0 mg/day) in combination in both syndromes. The inhibitory effect of the combined treatment was greater than that of the treatment with estrogen alone. Administration of testosterone propionate (25 mg/day) for 3 days resulted in suppression of the release of both gonadotropins in baseline level and in response to LH-RH in both syndromes, but the suppressive effect appeared to be less complete as compared with that of estrogen or estrogen-progesterone. It was thus verified that the feedback interaction between the pituitary gonadotropin release and sex steroids such as estrogen, estrogen-progesterone or testosterone was operative in the same fashion in the patients with Turner's syndrome and Klinefelter's syndrome.     

Oral thyrotropin-releasing hormone (TRH) test in acromegaly

The effects of 40 mg oral and 200 microgram intravenous TRH were studied in patients with active acromegaly. Administration of oral TRH to each of 14 acromegalics resulted in more pronounced TSH response in all patients and more pronounced response of triiodothyronine in most of them (delta max TSh after oral TRh 36.4 +/- 10.0 (SEM) mU/l vs. delta max TSH after i.v. TRH 7.7 +/- 1.5 mU/l, P less than 0.05; delta max T3 after oral TRH 0.88 +/- 0.24 nmol/vs. delta max T3 after i.v. TRH 0.23 +/- 0.06 nmol/l, P less than 0.05). Oral TRH elicited unimpaired TSH response even in those acromegalics where the TSH response to i.v. TRH was absent or blunted. In contrast to TSH stimulation, oral TRH did not elicit positive paradoxical growth hormone response in any of 8 patients with absent stimulation after i.v. TRH. In 7 growth hormone responders to TRH stimulation the oral TRH-induced growth hormone response was insignificantly lower than that after i.v. TRH (delta max GH after oral TRH 65.4 +/- 28.1 microgram/l vs. delta max GH after i.v. TRH 87.7 +/- 25.6 microgram/l, P greater than 0.05). In 7 acromegalics 200 microgram i.v. TRH represented a stronger stimulus for prolactin release than 40 mg oral TRH (delta max PRL after i.v. TRH 19.6 +/- 3.22 microgram/, delta max PRL after oral TRH 11.1 +/- 2.02 microgram/, P less than 0.05). Conclusion: In acromegalics 40 mg oral TRH stimulation is useful in the evaluation of the function of pituitary thyrotrophs because it shows more pronounced effect than 200 microgram TRH intravenously. No advantage of oral TRH stimulation was seen in the assessment of prolactin stimulation and paradoxical growth hormone responses.     

Comparison of LH release and luteal function in cyclic and LH-RH-treated anoestrous ewes pretreated with PMSG or oestrogen.

Pretreatment of seasonally anoestrous Clun Forest ewes with 750 i.u. PMSG or 50 microgram oestradiol benzoate 24 or 7 h respectively before a single injection of 150 microgram synthetic LH-RH significantly increased the release of LH compared to that after injection of 150 microgram LH-RH alone. Total LH release in the two "combined" treatments was approximately 70% of that found at a natural oestrus, compared to 25% for LH-RH alone. All but one of the treated ewes ovulated, but only those pretreated with PMSG consistently produced corpora lutea capable of elevating peripheral plasma progesterone concentrations although these were lower than those at natural mid-cycle. These progesterone concentrations were, however, comparable to those during the natural cycle when corrected for the higher metabolic clearance rate found during anoestrus.     

Absorption and metabolism of oral progesterone.

The absorption, metabolism, and clearance of progesterone from the peripheral circulation were investigated in five postmenopausal women after oral administration of 100 mg daily for five consecutive days. Maximal plasma concentrations of progesterone were observed within four hours after ingestion of the last dose, when the range (22.11-34.18 nmol/l; 696-1077 ng/100 ml) was comparable with that observed during the mid-luteal phase of the ovarian cycle. The surge in values lasted six hours, and progesterone concentrations remained raised for at least 96 hours. Of the three metabolites studied, the plasma concentrations of pregnanediol-3 alpha-glucuronide were most raised by treatment, the peak values ranging from 1097 nmol/l (54.9 microgram/100 ml) to over 2000 nmol/l (100 microgram/100 ml), which was the upper limit of the assay used. Concentrations of 17-hydroxyprogesterone were least raised, and the peak values ranged from 4.32 to 9.68 nmol/l (143-319 ng/100 ml). The plasma profile of 20 alpha-dihydroprogesterone most closely approximated that of progesterone, although the range of maximal values was lower (7.11-16.06 nmol/l; 228-514 ng/100 ml). Plasma concentrations of oestradiol were unchanged by giving progesterone. It is concluded that the increases in circulating concentrations of progesterone and the biologically active metabolite 20 alpha-dihydroprogesterone, and the duration of these increases, were sufficient to modulate the biochemistry of responsive tissues. Oral progesterone may thus have a therapeutic role, and this route of administration merits further investigation.     

Metabolic clearance and production rates of oestradiol and progesterone during pubertal and postpubertal development in gilts

The crossbred gilts studied were aged 80 days (prepubertal), 180 days (prepubertal or postpubertal) and 260 days (postpubertal or pregnant). Estimates of metabolic clearance rate (MCR) of oestradiol and progesterone were consistently less (21 and 27%) in plasma than in blood, and these differences were not influenced by age of gilt. The MCR (1/day per kg body weight) for oestradiol and progesterone in plasma was greater (P less than 0.05) for 80-day-old prepubertal gilts than for older gilts. The MCR values of oestradiol and progesterone were similar in 180-day-old and 260-day-old gilts independent of reproductive state. Production rate (PR) of oestradiol and progesterone increased with age (80-180 days), and age and reproductive state differences were much more pronounced for PR of progesterone than of oestradiol. These results support the hypothesis that a reduction in the MCR and an increase in PR of oestradiol and progesterone in the gilt are associated with the process of pubertal development, and changes in gonadal steroid concentrations appear not to alter the MCR of oestradiol and progesterone.     

Control of endometrial oxytocin receptor and uterine response to oxytocin by progesterone and oestradiol in the ewe

The effects of administration of progesterone and oestradiol on ovine endometrial oxytocin receptor concentrations and plasma concentrations of 13,14-dihydro-15-keto prostaglandin F-2 alpha (PGFM) after oxytocin treatment were determined in ovariectomized ewes. Ewes received progestagen pre-treatment, progesterone and/or oestradiol in 11 different treatment schedules. Progestagen pre-treatment decreased oxytocin receptor concentrations in endometrium from ewes treated subsequently with either progesterone for 5 days or progesterone for 5 days plus oestradiol on Days 4 and 5 of progesterone treatment. Oestradiol increased endometrial oxytocin receptor concentrations when administered on Days 4 and 5 of 5 days progesterone treatment. Progestagen pre-treatment followed by progesterone treatment for 12 days caused a large increase in oxytocin receptors and no further increase occurred when ewes were given oestradiol on Days 11 and 12, or when progesterone was withdrawn on Days 11 and 12, or these two treatments were combined. Oxytocin administration caused an increase in plasma PGFM concentrations in ewes which did not receive progestagen pre-treatment, and subsequently received progesterone treatment for 5 days and oestradiol treatment on Days 4 and 5 of progesterone treatment. Similarly treated ewes which received progestagen pre-treatment did not respond to oxytocin. Oxytocin administration also increased plasma PGFM concentrations in ewes which received progestagen pre-treatment followed by progesterone treatment for 12 days, progesterone treatment for 12 days plus oestradiol on Day 11 and 12 of progesterone treatment, progesterone withdrawal on Day 11 and 12, or progesterone withdrawal and oestradiol treatment combined. The results indicate that (1) progesterone pre-treatment affects oxytocin receptor concentrations in the endometrium and uterine responsiveness to oxytocin and (2) progesterone treatment alone for 12 days after a treatment which mimics a previous luteal phase and oestrus is sufficient to induce oxytocin receptors and increase oxytocin-induced PGF release. These results emphasize the importance of progesterone and provide information which can be used to form an hypothesis for control of luteolysis and oestrous cycle length in the ewe.     

Effect of treatment with progesterone and oestradiol when starting treatment with an intravaginal progesterone releasing insert on ovarian follicular development and hormonal concentrations in Holstein cows

Ovarian follicular development and concentrations of gonadotrophin and steroid hormones were studied in non-lactating Holstein cows following administration of progesterone (P(4)) or oestradiol benzoate (ODB) at the start of treatment with an intravaginal progesterone releasing insert (IVP(4)) in a 2 by 2 factorial experiment. Cows were treated at random stages of the oestrous cycle with an IVP(4) device (Day 0) and either no other treatment (n=8), 200 mg of P(4) IM (n=9), 2.0 mg of ODB IM (n=8) or both P(4) and ODB (n=9). Seven days later devices were removed and PGF(2alpha) was administered. Twenty-four hours later 1.0mg of ODB was administered IM. Oestrus was detected in 97.1% and ovulation in 64.7% (effect of treatment, P=0.41) of cows within 96 h of removing inserts. In the cows that ovulated, day of emergence of the ovulatory follicle was delayed (P<0.01) and more precise (P<0.05) in cows treated with ODB compared to the cows treated with P(4). Interval from wave emergence to ovulation and the diameter of the ovulatory follicle was less (P<0.05) in cows treated with ODB compared to cows treated with P(4). Combined treatment with P(4) and ODB at the time of starting treatment with an IVP(4) device did not significantly change the pattern of ovarian follicular development compared to treatment with ODB alone. Concentrations of LH and FSH in plasma were less in cows treated with ODB between Days 0 and 4 (P<0.05) while treatment with P(4) increased concentrations of FSH in plasma between Days 0 and 4 (P<0.05). When anovulatory cows were compared to ovulatory cows, diameters of follicles (P<0.001) and growth rate of follicles (P<0.01) were less in anovulatory cows between Days 7 and 9, while concentrations of FSH in plasma were greater (P<0.01), concentrations of LH similar (P>0.90) and concentrations of oestradiol were less (P=0.01) in the anovulatory cows between Days 4 and 10. Our findings support a hypothesis that ovarian follicular development following administration of P(4) or ODB at the start of treatment with an IVP(4) device differs. Anovulatory oestrus may have been associated with reduced maturity and/or later emergence of ovarian follicles.     

Hormonal regulation of oestrogen and progesterone receptors in cultured bovine endometrial cells.

Changes in the number of progesterone and oestradiol receptors in the endometrium are thought to play a role in the induction of luteolysis. The effect of oestradiol and progesterone on the regulation of their receptors in cultured bovine uterine epithelial and stromal cells was examined to determine the mechanisms involved in this process. Cells were obtained from cows at days 1-3 of the oestrous cycle and were cultured for 4 or 8 days in medium alone (RPMI medium + 5% (v/v) charcoal-dextran stripped newborn calf serum) or with oestradiol, progesterone or oestradiol and progesterone. At the end of culture, receptor binding was measured by saturation analysis. Specific binding of both [3H]ORG 2058 (16 alpha-ethyl-21-hydroxy-19-nor (6,7-3H) pregn-4-ene-3,20-dione) and [3H]oestradiol to epithelial and stromal cells showed high affinities (Kd = 1.1 x 10(-9) and 6 x 10(-10) mol l-1, respectively, for progesterone receptors; Kd = 5.5 x 10(-9) and 7 x 10(-10) mol l-1, respectively, for oestradiol receptors). In the stromal cells, oestradiol (0.1-10 nmol l-1) increased the number of oestradiol receptors from 0.21 +/- 0.06 to 0.70 +/- 0.058 fmol microgram-1 DNA and the number of progesterone receptors from 1.4 +/- 0.83 to 6.6 +/- 0.70 fmol microgram-1 DNA in a dose-dependent manner after 4 days of culture (P < 0.01). After culture for 8 days, the stimulatory effect of oestradiol increased. Progesterone (50 nmol l-1) had no effect on the number of oestradiol or progesterone receptors (P > 0.05). However, progesterone inhibited the stimulatory effect of oestradiol. In epithelial cells, the lower concentrations of oestradiol (0.1 and 1 nmol l-1) stimulated the number of progesterone receptors (P = 0.05) after 4 days culture, whereas the highest concentration of oestradiol (10 nmol l-1), progesterone (50 nmol l-1) and progesterone (50 nmol l-1) plus oestradiol (1 nmol l-1) had no effect. After culture for 8 days, the stimulatory effect of oestradiol decreased. In contrast to progesterone receptors, the number of oestradiol receptors increased with oestradiol concentration (P < 0.01). These data show that the number of progesterone receptors was higher in the stromal cells than in epithelial cells, whereas the number of oestradiol receptors was higher in the epithelial cells than in stromal cells. Oestradiol upregulates its own receptor and increases the number of progesterone receptors in both cell types in vitro, whereas progesterone has little effect, but inhibits the effects of oestradiol on progesterone receptors.     

Effect of in vivo prostaglandin treatment on 3H-PGF2alpha uptake in hamster corpora lutea.

Pregnant hamsters were administered (SC) prostaglandin or vehicle on the morning of the 4th day of pregnancy. Serum progesterone was significantly depressed (p less than .01) at 0.5, 2, and 6 hours after treatment with 100 microgram PGF2alpha. Serum progesterone levels were unchanged 2 hours and 6 hours after treatment with 100 microgram PGF2beta and 2 hours after treatment with 1 mg PGF2beta. Progesterone levels were depressed to less than 1 ng/ml 6 hours after treatment with 1 mg PGF2beta. The specific uptake of 3H-PGF2alpha in whole hamster corpora lutea was significantly depressed 2 hours and 6 hours following 100 microgram PGF2alpha treatment. A 15% depression in specific uptake occurred 0.5 hour post-treatment. Treatment with 100 microgram PGF2beta resulted in no change. Administration of 1 mg PGF2beta resulted in depressed 3H-PGF2alpha uptake at both 2 and 6 hours post-treatment. Prostacyclin (PGI2) treatment resulted in no change in either 3H-PGF2alpha specific uptake or serum progesterone 2 hours after 100 microgram treatment SC. These parameters were both reduced approximately 30% 6 hours post-treatment. Treatment with 6-keto-PGF1alpha resulted in a complete lack of measurable 3H-PGF2alpha uptake and serum progesterone levels less than 1 ng/ml at both 2 and 6 hours after treatment with 1 mg SC.     

Variability in the response of the rabbit uterus to progesterone as influenced by prolactin

Ovariectomized rabbits from different breeders were treated at different times of the year with prolactin alone or with progesterone and the production of uteroglobin by the uterus was studied. There were seasonal, strain and dose variables in the uterine response to prolactin and progesterone. Treatment with prolactin (at 1 mg/day) plus progesterone generally induced higher levels of uteroglobin production than did treatment with progesterone alone. The differences were greatest in the winter for Tennessee animals and in the spring for animals from the New Mexico and North Carolina colonies. Ovariectomy produced a decrease (P less than 0.01) in the concentration of cytosolic oestrogen and progesterone receptors, and prolactin treatment restored the concentration to oestrous control values. However, there were no seasonally dependent changes in the concentration of the receptors for any of the treatment groups. Increased doses of prolactin (2 mg/day) induced high levels of uteroglobin production and new proteins to appear in uterine secretions of long-term ovariectomized rabbits but much lower levels (10-11%) when given to pregnant does. Additional ovulations were also noted plus adverse effects on the embryos.     

Ovarian steroid involvement in endogenous opioid modulation of LH secretion in seasonally anoestrous mature ewes

In June, 16 mature ewes were ovariectomized and allocated to four groups: 1, saline; 2, naloxone; 3, progesterone implant plus naloxone; 4, oestrogen implant plus naloxone. Steroids were implanted at the time of ovariectomy. At 5 days after ovariectomy, the animals were intravenously infused with saline for 8 h and naloxone (50 mg/h) in saline for 8 h the following day. Three intact ewes were given naloxone in a similar way. During infusions and for 8 h on the day after naloxone, jugular venous blood samples were taken every 15 min and assayed for LH. Naloxone resulted in significant increases in mean LH concentration (P less than 0.01), LH episode frequency and episode height (P less than 0.05) in Group 3 ewes, but was without effect in any other group. These results provide evidence that the progesterone status of the ewe affects its response to naloxone, that progesterone negative feedback on LH release may be mediated by an opioid system, and that increased oestradiol negative feedback during seasonal anoestrus is unlikely to work via increased opioid inhibition of LH.