Effects of prostaglandins E2 and F2alpha (PGE2; PGF2alpha), trilostane, mifepristone, palmitic acid (PA), indomethacin (INDO), ethamoxytriphetol (MER-25), PGE2 + PA, or PGF2alpha + PA on PGE2, PGF2alpha, and progesterone secretion by bovine corpora lutea of mid-pregnancy in vitro

The effects of PGE2, PGF2alpha, trilostane, RU-486, PA, INDO, MER-25, PGE2, or PGF2alpha + PA on secretion of progesterone, PGE2, or PGF2alpha by bovine corpora lutea (CL) of mid-pregnancy in vitro for 4 and 8 hr was examined. Secretion of PGE2 and PGF2alpha increased with time in culture (P < or = 0.05). PGE2 and PGE2 + PA increased (P < or = 0.05) secretion of progesterone at 4 and 8 h, progesterone secretion was increased (P < or = 0.05) at 4 h; but not at 8 h (P > or = 0.05) by trilostane, mifepristone, PGF2alpha and PGF2alpha + PA, and was decreased at 8 h by PGF2alpha and PGF2alpha + PA. Indomethacin decreased (P < or = 0.05) secretion of PGE2, PGF2alpha, and progesterone at 4 and 8 h. Trilostane, PA, PGF2alpha, RU-486 and PGF2alpha + PA increased (P < or = 0.05) PGE2 at 4 h only. Palmitic acid decreased (P < or = 0.05) PGF2alpha at 4 h, while trilostane, RU-486, or MER-25 did not affect (P < or = 0.05) PGE2 of PGF2alpha secretion. It is concluded that PGE2 of luteal tissue origin is the luteotropin at mid-pregnancy in cows. Also, it is suggested that PA may alter progesterone secretion by affecting the inter conversion of PGE2 and PGF2alpha.

Effects of indomethacin, luteinizing hormone (LH), prostaglandin E2 (PGE2), trilostane, mifepristone, ethamoxytriphetol (MER-25) on secretion of prostaglandin E (PGE), prostaglandin F2alpha (PGF2alpha) and progesterone by ovine corpora lutea of pregnancy or the estrous cycle

Two experiments were conducted to determine the luteotropin of pregnancy in sheep and to examine autocrine and paracrine roles of progesterone and estradiol-17 beta on progesterone secretion by the ovine corpus luteum (CL). Secretion of progesterone per unit mass by day-8 or day-11 CL of the estrous cycle was similar to day-90 CL of pregnancy (P > or = 0.05). In experiment 1, secretion of progesterone in vitro by slices of CL from ewes on day-8 of the estrous cycle was increased (P < or = 0.05) by LH or PGE2. Secretion of progesterone in vitro by CL slices from day-90 pregnant ewes was not affected by LH (P > or = 0.05) while PGE2 increased (P < or = 0.05) secretion of progesterone. Day 8 ovine CL of the estrous cycle did not secrete (P > or = 0.05) detectable quantities of PGF2alpha or PGE while day-90 ovine CL of pregnancy secreted PGE (P < or = 0.05) but not PGF2alpha. Secretion of progesterone and PGE in vitro by day-90 CL of pregnancy was decreased (P < or = 0.05) by indomethacin. The addition of PGE2, but not LH, in combination with indomethacin overcame the decreases in progesterone by indomethacin (P < or = 0.05). In experiment 2, secretion of progesterone in vitro by day-11 CL of the estrous cycle was increased at 4-h (P < or = 0.05) in the absence of treatments. Both day-11 CL of the estrous cycle and day-90 CL of pregnancy secreted detectable quantities of PGE and PGF2alpha (P < or = 0.05). In experiment 1, PGF2alpha secretion by day-8 CL of the estrous cycle and day-90 ovine CL of pregnancy was undetectable, but was detectable in experiment 2 by day-90 CL. Day 90 ovine CL of pregnancy also secreted more PGE than day-11 CL of the estrous cycle (P < or = 0.05), whereas day-8 CL of the estrous cycle did not secrete detectable quantities of PGE (P > or = 0.05). Trilostane, mifepristone, or MER-25 did not affect secretion of progesterone, PGE, or PGF2alpha by day- 11 CL of the estrous cycle or day-90 CL of pregnancy (P > or = 0.05). It is concluded that PGE2, not LH, is the luteotropin at day-90 of pregnancy in sheep and that progesterone does not modify the response to luteotropins. Thus, we found no evidence for an autocrine or paracrine role for progesterone or estradiol-17 36 on luteal secretion of progesterone, PGE or PGF2alpha.

Molecular structures and conformational studies of triarylcyclopropyl and related nonsteroidal antiestrogens

Molecular structures and conformational characteristics of a series of 1,1-dichloro-2,2,3-triarylcyclopropanes (DTACs), which were reported previously to be distinctly antiestrogenic and inhibitors of the estrogen-receptor-positive MCF-7 human breast cancer cells in culture, are reported. In addition, structural and conformational features of the DTACs were compared to the first-known nonsteroidal antiestrogen, MER25, and the clinically useful antiestrogen Tamoxifen. The molecular structures of four DTAC compounds were determined by X-ray diffraction. Crystallographic structures show that the DTAC molecules have nearly the same relative conformation for the three aryl rings which is designated as a "nonpropeller" conformation in contrast to the observed "propeller" conformation for the three rings in all known triarylethylenes. Systematic conformational searches were performed to find the conformational preferences of DTACs, MER25, and Tamoxifen using idealized model compounds built from their respective crystal structure. Energy-minimization and conformational-search studies demonstrated that all DTAC molecules have a common, single global minimum energy conformer for their central core containing the dichlorotriarylcyclopropyl system, which is similar to that found in their crystal structures. Conformational search of MER25 showed that the molecule can assume a number of low-energy conformers of which two, one anti (A1) and one gauche (G1A), have about the same energy. The anti conformation is similar to the one observed in its crystal structure and resembles the estrogenic E-isomer of Tamoxifen, while the lowest energy gauche conformer of MER25 resembles more closely the antiestrogenic Z-isomer of Tamoxifen. NMR spectroscopic analysis of MER25 showed that the molecule exists predominantly in the anti conformation in solution. A comparative review of the structural features and bioactivities of Tamoxifen, DTACs, and MER25 provides a possible explanation for their low estrogen receptor binding affinity which is common to these compounds together with their antiestrogenic activity.

The aversive and hypophagic effects of estradiol

Estradiol is known to reduce food intake in many species. Recent studies have also shown that estradiol can function as an unconditioned stimulus in taste aversion paradigms, suggesting that it induces nausea and malaise in rats and mice. The experiments reported here compared the hypophagic and aversive effects of estradiol. Using mice as subjects, the first investigation examined the taste aversion properties of the estradiol receptor antagonist MER-25, which is estrogenic with respect to feeding. MER-25 induced a strong taste aversion, contrary to a previous report. Second, progesterone, which counteracts the hypophagic effects of estradiol, did not disrupt the taste aversion induced by estradiol in mice. The third investigation used the Mongolian gerbil, a species in which estradiol increases food intake, in contrast to other species. Despite increasing food intake, estradiol induced a conditioned taste aversion in the gerbil similar to that seen in rats and mice. Taken together, these results indicate that the feeding and aversive effects of estrogen are mediated by different mechanisms.

Regulation of immunoreactive inhibin patterns in baboon pregnancy: maternal, placental, and fetal considerations

To better understand the sources and regulation of circulating inhibin during primate pregnancy, immunoreactive inhibin was measured in sera obtained from the maternal saphenous vein, uterine vein, and the fetus at varying times of baboon pregnancy. In both intact and fetectomized (fetus removed on day 100 of gestation; term = 184 days) animals, maternal serum inhibin concentrations were relatively constant between day 80 (first sampling day) and day 110 of gestation, after which they then steadily increased until days 155-165 (end of sampling). The increase in inhibin concentrations was significantly less in the fetectomized animals than in the intact baboons. Restoration of estrogen levels in the fetectomized animals did not significantly alter the circulating inhibin concentrations. Similarly, administration of the estrogen antagonist MER-25 to intact animals in the last trimester had no effect on maternal serum inhibin concentrations. Inhibin concentrations in uterine venous blood collected on day 100 of gestation were not significantly different from those in the maternal saphenous vein. However, the inhibin concentrations of uterine venous blood collected late in gestation (days 155-165) in either intact or fetectomized animals were significantly higher than the corresponding maternal venous concentrations, suggesting that the uteroplacental tissue becomes a source of circulating inhibin during the third trimester of pregnancy. Consistent with this suggestion was the detection of inhibin alpha-subunit mRNA in the placentae of intact or fetectomized animals obtained late in pregnancy, but its absence at midgestation. Immunoreactive inhibin concentrations were about 16 times higher (6500 +/- 831 mu Leq/mL) in fetal blood than in maternal blood (411 +/- 23 mu Leq/mL) at midgestation. The fetal blood concentrations significantly decreased to about 2800 mu Leq/mL by days 160-165 of gestation, but were still greater than those in the mother (approximately 1000 mu Leq/mL). The umbilical arterial and venous concentrations were the same as the fetal blood concentration of inhibin. The role of the baboon fetal adrenal in inhibin production was studied. Fetal adrenals collected from days 59, 135, and 167 of gestation contained the mRNA for the inhibin alpha-subunit in relatively high abundance. The in utero administration of ACTH for 30 min to five fetuses at midgestation (days 100-110) apparently did not alter the fetal concentration of immunoreactive inhibin. In summary, maternal serum inhibin levels increase during the last trimester of baboon pregnancy. This is suggested to be due to an increasing contribution of placental inhibin secretion, which is regulated not by placental estrogen production but, perhaps, by placental growth.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of decidual induction in rats by clomiphene and tamoxifen

The objective of this study was to characterize the estrogen action that confers endometrial sensitization to nontraumatic deciduogenic stimuli by use of antiestrogens. Tamoxifen, ethamoxytriphetol, and clomiphene and its two component enantiomers inhibited decidual induction in pseudopregnant rats when administered 17 h before pyrathiazine. Unexpectedly, clomiphene (250 micrograms/rat) and tamoxifen (25 micrograms/rat) proved inhibitory at all times up to and including the time of induction. Clomiphene, administered in the hours preceding decidual induction, inhibited the increase of ornithine decarboxylase activity, which normally marks the end of the induction phase. Clomiphene had no inhibitory effect on the availability or receptor binding of progesterone. Clomiphene also inhibited implantation of blastocysts when administered at the time of their adherence to the uterus. The inhibition by antiestrogens of decidual induction could not be explained on the basis of the current understanding of mechanisms of estrogen action. The discrepancies were that no latent period between the time of antiestrogen administration and decidual induction was observed and no difference was observed in the inhibitory activities of the isomers of clomiphene.

Effects of nonsteroidal antiestrogens in the in vitro rat uterus

We have studied the effect of nonsteroidal antiestrogens on rat uterine contractions induced by oxytocin (8 nmol/l), methacholine (10 mumol/l), prostaglandin F2 alpha (1 mumol/l), KCl (60 mmol/l) and CaCl2 (6 mmol/l). In a concentration-dependent way, the antiestrogens tamoxifen, clomiphene, nafoxidine and ethamoxytriphetol inhibited the amplitude and frequency of the oxytocin-induced contractions and the contraction produced by CaCl2. At a concentration of 30 mumol/l the four drugs inhibited the contractions induced by methacholine and prostaglandin F2 alpha. They also relaxed the tonic contraction to KCl in a concentration-dependent way. This action was partially counteracted by CaCl2 (0.1-10 mmol/l). Bay k 8644 (0.3 nmol/l to 3 mumol/l) only partially reversed the inhibition by ethamoxytriphetol (0.1 mmol/l) of CaCl2 (6 mmol/l)-induced contractions. The steroidal antiestrogen, ICI 164,384, which lacks agonist activity, had an inhibitory effect (44 +/- 4%, n = 7) on KCl-induced contractions only at a concentration of 0.1 mmol/l. However, the quaternary analogue of tamoxifen (tamoxifen ethyl bromide) produced 86 +/- 3% relaxation of the KCl-induced contracture (IC50 1.52 +/- 0.1 mumol/l, n = 10) and this effect was counteracted by addition of CaCl2. Taken together the results indicate that the inhibitory effects of nonsteroidal antiestrogens on rat uterine contractions could be mediated by an action to block Ca2+ entry through an agonist action on extracellular estrogen receptors.

Regulation of placental low-density lipoprotein uptake in baboons by estrogen: dose-dependent effects of the anti-estrogen ethamoxytriphetol (MER-25)

In the present study, increasing amounts of the anti-estrogen 1-(p-2-diethylaminoethoxyphenyl)-1-phenyl-2-p-methoxyphenoletha nol (MER-25) were administered to pregnant baboons (Papio anubis) to block the action of endogenous estrogen and to determine effect on placental low-density lipoprotein (LDL) uptake. Pregnant baboons were untreated (n = 8) or received MER-25 orally at a dosage of 25 (n = 10), 50 (n = 8), or 75 (n = 4) mg/kg BW daily on Days 140-170 of gestation (term = 184 days). Placentas were removed on Day 170 of gestation and villous tissue was dispersed with 0.1% collagenase. Placental cells (10(6] were incubated in Medium 199 for 12 h at 37 degrees C with increasing amounts of 125I-LDL, with or without a 100-fold excess of unlabeled baboon LDL. Mean (+/- SEM) placental uptake (ng/micrograms cell protein) of 125I-LDL was 55% (6.4 +/- 1.0), 75% (3.6 +/- 0.7), and 81% (2.7 +/- 0.2) lower (p less than 0.001) in baboons that received MER-25 in doses of 25, 50, and 75 mg/kg BW, respectively, than in untreated baboons (14.2 +/- 1.3 ng/micrograms cell protein). Maximal effect occurred with 50 mg MER-25, because LDL uptake was not further decreased with greater levels of MER-25. Dissociation constants for placental LDL uptake, as determined by Scatchard analysis, were unaltered by anti-estrogen treatment. The amount of 125I-LDL degradation by placental cells of untreated and MER-25-treated baboons was proportional to LDL uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of the baboon fetal pituitary-adrenocortical axis at midgestation by estrogen: adrenal delta 5-3 beta-hydroxysteroid dehydrogenase and 17 alpha-hydroxylase-17,20-lyase activity

We have recently demonstrated that treatment of pregnant baboons with androstenedione (delta 4 A) at midgestation to increase estrogen production induced a pattern of placental cortisol (F) metabolism which was similar to that at term and resulted in de novo F production by the fetus, presumably by activation of the fetal hypothalamic-pituitary-adrenocortical axis. The present study was designed to examine the subcellular events in the fetal adrenal that were apparently stimulated by estrogen-induced alterations in transplacental corticosteroid metabolism. Therefore, we determined the effects of estrogen treatment at midgestation and removal of estrogen action near term on the specific activity of the rate-limiting enzymes delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta HSD) and 17-hydroxylase-17,20-lyase (17 alpha-OHase). Fetal adrenals were obtained on day 100 (n = 11) or day 165 (n = 11) of gestation (term = day 184) from untreated animals, on day 100 from animals receiving delta 4 A daily between days 70-100 (n = 9) to increase placental estrogen production, and on day 165 from baboons treated daily between days 130-164 with antiestrogen ethamoxytriphetol (MER-25; n = 7). The activity of 17 alpha-OHase was determined by incubating adrenal microsomes (105,000 x g) with [3H] progesterone, NAD+, and NADH in phosphate buffer. The radiolabeled products 17-hydroxyprogesterone, delta 4 A, and testosterone were purified, and enzyme activity expressed as picograms of product per min/mg tissue. The activity of 3 beta HSD was determined by incubating adrenal microsomes with [3H]pregnenolone and NAD+ in phosphate buffer. The radiolabeled progesterone product was purified, and enzyme activity was expressed as nanograms per min/mg tissue. Treatment with delta 4 A increased estrogen concentration at midgestation 3-fold to levels comparable to those measured near term. Although fetal adrenal weight was greater at term than at midgestation (p less than 0.05), weight was not increased by delta 4 A treatment. The specific activity (mean +/- SE) of fetal adrenal 17 alpha-OHase at midgestation (181 +/- 29) was increased (P less than 0.05) 3-fold by treatment with delta 4 A to levels (591 +/- 105) comparable to those in adrenal microsomes prepared from untreated animals near term (816 +/- 130). Enzyme activity in adrenals of MER-25-treated baboons was 40%, but not significantly lower than that in term controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of adrenocorticotropin-stimulated baboon fetal adrenal dehydroepiandrosterone formation in vitro by estrogen at mid- and late gestation

We have reported that ACTH stimulation of dehydroepiandrosterone (DHA) formation by the baboon fetal adrenal at midgestation was suppressed by estrogen. Because fetal adrenal regulation changes with advancing gestation, the action of estrogen on fetal adrenal steroidogenesis may also be dependent on the degree of fetal adrenal maturation. We examined this possibility in the present study by determining the effects of ACTH and estrogen on DHA formation by adrenal cells of fetuses obtained from baboons at mid- and late gestation and from animals administered the antiestrogen MER-25 throughout late gestation. Because low density lipoprotein (LDL) provides substrate for the fetal adrenal, we also determined whether the effect of estrogen was mediated by LDL uptake. Adrenals were removed from baboon fetuses on day 100 (midgestation; n = 7) and day 170 (late gestation; n = 6; term, day 184) of gestation from untreated animals and on day 170 from fetuses whose mothers were treated with MER-25 on days 140-170 (25 mg/kg BW.day; n = 7). Cells were dispersed with 0.2% collagenase and incubated at 37 C for 3 h in 4 ml medium 199 with 10 nM ACTH, 10(-6) M estradiol and/or 500 micrograms LDL. The secretion of DHA into medium was determined by RIA. At midgestation, mean (+/- SE) basal DHA formation (nanograms per 10(5) cells/3 h) was 5.8 +/- 2.1, and DHA was increased (P less than 0.01) by ACTH to 20.0 +/- 5.9. Although estradiol alone had no effect, estradiol prevented the increase in DHA obtained with ACTH. Basal DHA production by adrenals of late gestation (0.7 +/- 0.3 ng/10(5) cells) was lower (P less than 0.01) than at midgestation. ACTH increased (P less than 0.01) DHA in a comparable manner near term in the presence (2.0 +/- 0.4) or absence (1.7 +/- 0.4) of estradiol. Thus, in contrast to day 100, estrogen did not attenuate the action of ACTH on adrenal cells on day 170. In fetal adrenal cells obtained on day 170 from MER-25-treated baboons, DHA formation (1.4 +/- 0.6 ng/10(5) cells) was comparably increased (P less than 0.05) to 2.4 +/- 0.2 and 3.0 +/- 0.5 ng/10(5) cells by ACTH in the absence or presence of estradiol. Thus, ACTH remained effective in enhancing DHA by adrenal cells of fetuses exposed in utero to antiestrogen. DHA formation by adrenals of midgestation was increased (P less than 0.05) to 15.4 +/- 4.8 and 27.4 +/- 7.5 ng/10(5) cells, respectively, by LDL and ACTH plus LDL.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of steroidal and nonsteroidal antiestrogens on the growth of a tamoxifen-stimulated human endometrial carcinoma (EnCa101) in athymic mice

Tamoxifen (TAM), a nonsteroidal antiestrogen, is used in the adjuvant treatment of breast cancer. Previous studies, however, have indicated that some human breast and endometrial tumors are stimulated to grow with TAM in the athymic mouse. One such TAM-stimulated tumor is the EnCa101 human endometrial adenocarcinoma. Our aim was to evaluate the ability of different doses of TAM or other nonsteroidal antiestrogens to stimulate the growth of EnCa101 tumors in athymic mice. Additionally we have evaluated less estrogenic antiestrogens (two steroidal antiestrogens, RU 39,411 and ICI 164,384, and two nonsteroidal antiestrogens, keoxifene and MER-25) for their ability to inhibit TAM-stimulated growth. All experiments were done in ovariectomized athymic mice transplanted in the axillary mammary fat with 1-mm3 pieces of EnCa101 tumor. Sustained release preparations (0.5-2.0-cm Silastic capsule or 5-mg TAM cholesterol pellet) of TAM caused similar tumor growth. The growth rate was not altered by an additional daily i.p. injection of 1 mg TAM in 0.1 ml peanut oil. A 3-mg TAM daily dose was toxic. Four weeks of treatment (100-micrograms s.c. injections, every other day) with nonsteroidal antiestrogens, trioxifene mesylate, enclomiphene, or nafoxidine stimulated tumor growth. However, keoxifene stimulated this tumor to a lesser degree than TAM and partially inhibited TAM-stimulated growth. ICI 164,384 showed no stimulatory activity (1-mg s.c. injections every other day) alone compared to controls but inhibited TAM-stimulated (0.25-cm Silastic capsule) growth. In a parallel experiment, RU 39,411 (1-mg s.c. injections every other day) stimulated EnCa101 to grow. In contrast when RU 39,411 was administered in a sustained release preparation (2.0-cm Silastic capsule) there was no stimulatory growth compared to controls. Additionally RU 39,411 inhibited TAM-stimulated growth, but the low-potency antiestrogen, MER-25, was less effective in this regard. These data suggest that less "estrogenic" antiestrogens can inhibit TAM-stimulated tumor growth in vivo. Thus these compounds or derivatives may prove useful as a second-line endocrine therapy should TAM-stimulated tumor growth occur in the clinic.

Regulation of progesterone biosynthesis by estrogen during baboon pregnancy: placental mitochondrial cholesterol side-chain cleavage activity in antiestrogen (ethamoxytriphetol, MER-25)-treated baboons

We determined whether the reduction in placental progesterone (P4) production observed after administration of the antiestrogen ethamoxytriphetol (MER-25) to pregnant baboons was associated with a decline in activity and/or content of the placental mitochondrial cholesterol side-chain cleavage system (P-450scc). Pregnant baboons (Papio anubis) were untreated (n = 9) or administered MER-25 (25 mg/kg BW, orally; n = 6) daily on days 140-170 of gestation (term = 184 days). Placentas were obtained by cesarean section on day 170 of gestation, and P-450scc activity and cytochrome P-450 content were determined on mitochondria-rich fractions. Administration of MER-25 to pregnant baboons resulted in a 40% reduction (P less than 0.01, by Student's t test) in the mean (+/- SE) peripheral serum P4 concentration (6.3 +/- 0.3 ng/ml) compared to that in untreated (10.4 +/- 0.3 ng/ml) baboons. P-450scc activity, as determined by formation of pregnenolone (P5) and P4 during a 30-min incubation (picomoles per mg protein), was 37% lower (P less than 0.01) in placental mitochondria obtained from MER-25-treated baboons (179.8 +/- 25.0) than in that from untreated (285.4 +/- 13.4) baboons. Mitochondrial cytochrome P-450 content, assessed by spectral analysis, was 28% lower (P less than 0.02) in antiestrogen-treated (46.7 +/- 2.1 pmol/mg protein) than in untreated (64.8 +/- 5.2 pmol/mg protein) baboons. The initial (time zero) free cholesterol content (nanomoles per mg protein) of mitochondrial-rich preparations was not significantly different in antiestrogen-treated (189.3 +/- 13.0) and untreated (225.0 +/- 15.1) animals. Collectively, these results suggest that the decline in placental P4 production observed in baboons in response to MER-25 occurs at least in part as a result of a decrease in cytochrome P-450scc activity. The loss in P-450scc activity appears to be an intramitochondrial event and not a result of depletion of the total mitochondrial cholesterol pool. We propose, therefore, that one mechanism by which estrogen may regulate the production of P4 by the placenta during primate pregnancy is via the maintenance of placental mitochondrial cytochrome P-450, the terminal oxidase of cytochrome P-450scc.

Deciduoma formation in rats treated neonatally with the anti-estrogens, tamoxifen and MER-25

Female rats of the T strain were given single daily injections of 100 micrograms and 200 micrograms of tamoxifen (Tx) and MER-25 (MER) for 5 days beginning on the day of birth (DAY 1). When sacrificed on Day 60, the Tx-treated rats (Tx rats) exhibited continued vaginal diestrus, whereas the females given MER or the vehicle alone showed regular estrous cycles. Ovaries from Tx rats were polyfollicular without corpora lutea, while those from MER rats, as well as from the controls given the vehicle alone, invariably contained both follicles and corpora lutea. In Tx rats, the uteri underwent atrophy, containing few uterine glands in an endometrium largely occupied by fibroblasts. Decidual response of the uterus to intraluminal oil instillation was markedly reduced in Tx rats given an appropriate regimen of progesterone and estradiol injections following ovariectomy on Day 60. By contrast, MER given neonatally had little effects on decidualization. Since ovariectomy on Day 10 brought about no amelioration of the decidualization in Tx rats, it is suggested that the lowered deciduogenic responsiveness to the instillation was caused by a direct action of Tx on the uterus of neonatal rats rather than by a Tx-induced alteration of hypothalamo-hypophyseal-ovarian system. Differences in effect on the female reproductive system between Tx and MER were discussed.

Effect of the antiestrogen ethamoxytriphetol (MER-25) on placental low density lipoprotein uptake and degradation in baboons

The present study determined if the decline in placental progesterone (P4) production that results from administration of the antiestrogen ethamoxytriphetol (MER-25) to pregnant baboons results from a change in placental low density lipoprotein (LDL) uptake and/or degradation. Pregnant baboons (Papio anubis) were untreated (n = 10) or received MER-25 (25 mg/kg BW, orally; n = 10) daily on days 140-170 of gestation (term, 184 days). Placentas were removed by cesarean section on day 170 of gestation, and villous tissue was dispersed with 0.1% collagenase at 37 C for 40 min. Placental cells (10(6)) were incubated in medium 199 (pH 7.2) for 12 h at 37 C with increasing amounts (5-100 micrograms) of [125I]LDL, with or without a 100-fold excess of unlabeled baboon LDL. Mean (+/- SE) peripheral serum P4 concentrations on days 140-170 of gestation were 51% lower (P less than 0.01) in MER-25-treated (5.7 +/- 0.3 ng/ml) than in untreated (11.6 +/- 0.5 ng/ml) baboons. The uptake of LDL was 56% lower (P less than 0.01) in placental cells from antiestrogen-treated (6.3 +/- 1.6 ng/micrograms cell protein) than in those from untreated (14.4 +/- 1.9 ng/micrograms cell protein) baboons. The dissociation constants for placental LDL uptake, as assessed by Scatchard analysis, however, were similar in untreated (0.80 microgram/ml) and MER-25-treated (0.76 microgram/ml) animals. The amount of [125I]LDL concomitantly degraded by cells from baboons that received MER-25 was 54% of that degraded by cells from untreated controls. The relative decline in LDL degradation by cells of antiestrogen-treated baboons was proportionate to the decline in overall LDL uptake. The results indicate, therefore, that antiestrogen treatment decreased the amount of placental LDL uptake, but did not change the affinity for the lipoprotein. We suggest that the decline in placental P4 production elicited in pregnant baboons by antiestrogen results, at least in part, from subnormal LDL uptake. We propose that one of the mechanisms by which estrogen regulates the biosynthesis of P4 by the placenta during baboon pregnancy is by increasing receptor-mediated placental cell uptake of cholesterol in the form of LDL. Estrogen, therefore, may regulate LDL uptake by the placenta and thus the availability of cholesterol for P4 biosynthesis via the LDL pathway.

Transuterofetoplacental conversion of pregnenolone to progesterone in antiestrogen-treated baboons

The present study was designed to characterize the dynamics of progestin metabolism peripherally and across the uterus during normal baboon pregnancy and to determine whether the decline in placental progesterone (P4) production which results from administration of the antiestrogen ethamoxytriphetol (MER-25) to baboons reflects a decrease in conversion of pregnenolone (P5) to P4 and thus delta 5-3 beta-hydroxysteroid dehydrogenase activity. To examine this possibility, the conversion of [3H]P5 to [3H]P4 was determined by the constant infusion method on day 100 (midgestation) and day 175 (near term) of gestation in baboons that received MER-25 (25 mg/day X kg BW, po) on days 95-100 or 140-175 (term = 184 days). Baboons were sedated with ketamine HCl, then received a constant iv infusion of [3H]P5 (1.0 mu Ci/0.388 ml X min) and [14C]P4 (0.2 mu Ci/0.388 ml X min for 110 min. Radiolabeled progestins were purified from blood samples withdrawn from saphenous, uterine, and umbilical vessels, and the MCR of P4 and P5, uterine extraction of P5, and transfer constants (rho) for the peripheral, transuterofetoplacental, and transuteroplacental conversion of P5 to P4 were determined. The formation of P4 from P5 by incubates of placental cells obtained on day 175 from untreated and MER-25-treated baboons was also assessed. During normal baboon pregnancy the mean (+/- SE) % P5 extracted (i.e. metabolized) by the uterus was 31.0 +/- 3.3 at midgestation and 45.7 +/- 5.6 late in gestation. Peripheral and transuterofetoplacental rho values of P5 to P4 in untreated baboons were 6.9 +/- 1.8% and 37.3 +/- 7.9%, respectively, at midgestation and 6.1 +/- 0.6% and 46.8 +/- 10.1%, respectively, near term. The transuteroplacental rho of P5 to P4 was only slightly lower than the transuterofetoplacental values, indicating minimal conversion of P5 to P4 by the fetus. The peripheral contribution of P5 production to the total production rate of P4 at term in baboons was 1%. The contribution of uteroplacental conversion of P5 to P4 to the total conversion of P5 to P4 at midgestation was estimated to be 22%. MER-25 caused a 53% decline (P less than 0.01) in serum P4 concentrations from a mean (+/- SE) of 12.5 +/- 2.4 ng/ml during the pretreatment period to 5.4 +/- 0.3 ng/ml between days 140 and 175 of gestation.(ABSTRACT TRUNCATED AT 400 WORDS)

Fetal regulation of transplacental cortisol-cortisone metabolism in the baboon

We determined the role of the fetus and estrogen on transuteroplacental cortisol (F)-cortisone (E) metabolism in the baboon (Papio anubis). The interconversion of F-E at mid-gestation (day 100; term = day 184) was compared with that in animals near term (day 170) in which the fetus, but not the placenta, was removed (fetectomy) on day 100 and that in baboons treated daily between days 140 and 170 of gestation with the antiestrogen ethamoxytriphetol [1-(p-diethylamino-ethoxyphenol)1-phenyl-2-p-methoxyphenolethan ol (MER-25)]. In fetectomized animals at term, transuteroplacental conversion of E to F (30%) exceeded (P less than 0.05) that of the reverse reaction (7%). This pattern of metabolism was significantly different from that measured in intact pregnant animals at term, in which oxidation of F to E (28%) exceeded reduction of E to F (4%). In contrast, placental metabolism in fetectomized baboons at term was similar to that in pregnant animals at mid-gestation, in which conversion of F to E (20%) was lower (P less than 0.05) than reduction of E to F (39%). Treatment of intact pregnant baboons with MER-25 also resulted in a pattern of F-E metabolism across the placenta at term which was similar to that measured at midgestation but different from that in untreated baboons at term. Collectively, our findings show that the striking alteration in F-E interconversion from reduction (E to F) at midgestation to oxidation (F to E) by term, as measured across the placenta in vivo during the second half of baboon pregnancy, does not occur in animals lacking a fetus or in intact baboons in which the action of estrogen was inhibited. Therefore, we suggest that the fetus and/or the hormones of pregnancy that are dependent upon the fetus (i.e. estrogen) regulate transuteroplacental corticosteroid metabolism.

Regulation of progesterone formation by human placental cells in culture

In the present study, a culture system of human placental cells was established to examine the role of estrogen and androgen in progesterone (P4) formation. Normal human placentae were obtained at term, and cells were dispersed in Hank's Balanced Salt Solution (5 ml/g tissue) containing 0.1% collagenase, 0.1% hyaluronidase, 0.01% deoxyribonuclease, and 1% fetal bovine serum for 2 h at 37 C. Dispersed placental cells (10(6) cells/ml) were placed in medium 199 with modified Earle's salts (pH 7.4) containing 10% fetal bovine serum, 12.5 mM HEPES buffer, 26 mM NaHCO3, and 40 micrograms/ml Gentamycin-SO4 and incubated for 72 h at 37 C and 5% CO2 in air to allow cell attachment. Medium was then changed (time zero), and P4 formation was studied thereafter. Culture of placental cells for 96 h resulted in linear increases in P4 and estradiol (E2) formation, indicating the maintenance of cell viability and steroidogenic function. Mean +/- SE P4 formation at 48 h was 246 +/- 16 pg/micrograms DNA. To assess the role of estrogen on P4 formation, placental cells were incubated for a period of 48 h with various amounts (10(-7)-10(-4)M) of the antiestrogen ethamoxytriphetol (MER-25), the aromatase inhibitor 4-hydroxyandrostenedione (4-OHA), and/or E2. Both MER-25 and 4-OHA resulted in a dose-dependent decline (P less than 0.01) in P4 formation (greater than 80% decline at 10(-4)M MER-25 or 4-OHA). The marked reduction in P4 formation caused by 4-OHA alone was reversed by concomitant addition of E2; however, E2 alone had no effect. To assess the role of androgens on P4 formation, cells were incubated for 48 h with increasing amounts (10(-7)-10(-4)M) of androstenedione, dehydroepiandrosterone (DHA), or dihydrotestosterone. Although the formation of E2 was enhanced by DHA, formation of P4 was not affected by the aromatizable androgens DHA or androstenedione or the nonaromatizable dihydrotestosterone. The decline in P4 formation by human placental cells in culture elicited by MER-25 or 4-OHA supports the hypothesis of a regulatory role for estrogen in placental P4 formation during human pregnancy. The lack of effect of exogenous estrogen suggests that the action of estrogen on P4 formation may be permissive.

An in vitro demonstration of oestrogenicity with potential for exploitation as a quantitative assay for oestrogenic potency

The pre-implantation embryo of the mouse undergoes a histochemically detectable change in the properties of its trophoblastic cell-surface coat in the immediate pre-implantation period. This change is oestrogen-dependent in vivo and can be induced in vitro in a concentration-dependent manner by oestradiol-17 beta. There is evidence that this coat change is of functional importance in the process of implantation, and its demonstration is of potential value as the basis of an in vitro assay of oestrogenicity.

The relationship of estrogen to placental steroidogenesis in the baboon

In previous studies in pregnant baboons, estrogen deprivation produced by the administration of the estrogen antagonist MER-25 resulted in a decline in plasma progesterone. In the present study, pregnant baboons in whom the corpus luteum-bearing ovary was removed early in pregnancy were used to distinguish between a luteal or placental effect of this estrogen deprivation. MER-25, administered from days 35 through 48 of pregnancy, resulted in a significant decline in plasma progesterone, indicating a direct placental action of estrogen deprivation on progesterone production. In a second experiment using intact pregnant baboons, concomitant administration of the nonsteroidal estrogen diethylstilbestrol (DES) prevented the inhibitory effect of MER-25 on placental progesterone, indicating that the effect was due to antiestrogenic action of MER-25 and not to some other pharmacological effect of the antagonist. Since DES administration alone had no effect on plasma progesterone levels, the role of estrogen may be a permissive action. The administration of MER-25 did not inhibit estradiol production in intact pregnant baboons with or without corpora lutea. When DES was administered to intact pregnant baboons, alone or together with MER-25, there was a significant decrease in plasma estradiol concentrations, which was only reversed after the cessation of treatment. These studies indicate that estrogen, perhaps by different mechanisms, may be important in the regulation of placental estradiol and progesterone production in the primate.

Possible mechanisms for the agonist actions of tamoxifen and the antagonist actions of MER-25 (ethamoxytriphetol) in the mouse uterus

Experiments were conducted to determine why tamoxifen, a non-steroidal antiestrogen, is uterotrophic in mice, whereas MER-25 (ethamoxytriphetol), a structurally related compound, is antiuterotrophic. Initial experiments indicated that the pituitary was not required for a uterotrophic response in mice to either estradiol (E2), tamoxifen (TAM), or 4-hydroxytamoxifen (4-OH-TAM) MER-25 was not uterotrophic in mice but was capable of completely inhibiting the uterotrophic responses of mice to estrogens (E2) as well as antiestrogens (TAM and 4-OH-TAM); this inhibition was reversible by increasing the dose of the antiestrogen (TAM). The relative binding affinities (RBA) of TAM, 4-OH-TAM, and MER-25 to mouse uterus estrogen receptor (ER) and mouse liver antiestrogen binding sites (AEBS) were compared to determine whether either (or both) of these sites mediate the biological effects of these compounds. E2 is arbitrarily assigned an RBA of 100 for ER; similarly, TAM is assigned an RBA of 100 for AEBS. MER-25 bound to AEBS with an RBA of 8.9 and to ER with an RBA of less than 0.06; in contrast, TAM and 4-OH-TAM bound to AEBS with RBAs of 100 and 53, respectively, and to ER with RBAs of 2 and 131, respectively. Five other compounds that had similar RBAs as MER-25 for AEBs (RBAs in the range 4-9) and for ER (RBAs less than 0.06) were tested for their antiuterotrophic activities in vivo against both estrogen (E2) and antiestrogen (TAM) in ovariectomized mice. None of these compounds were antiuterotrophic against either estradiol or tamoxifen (P less than 0.01), nor were any of the compounds uterotrophic in mice. These data suggest that differences in the biological actions of tamoxifen and MER-25 in mice are not mediated through AEBS and are most likely due to differences in their interactions with ER.

Effect of perinatal antisteroid treatment on territorial marking behavior in the mongolian gerbil

Sex differences have been observed in the perinatal sexual differentiation of the neural substrate which regulates territorial marking behavior in the Mongolian gerbil. The present study examines the relative contribution of prenatal and postnatal steroid environment to sexual differentiation in the male and androgenized female using territorial marking behavior as an endpoint. Selective suppression of steroid effects in the pre- and postnatal period was accomplished with the antiandrogen flutamide or the antiestrogen MER-25. Treatment was given prenatally (for 5 days before expected parturition), on the day of birth, and postnatally (to day 10) or prenatally and on the day of birth only. Animals without postnatal antisteroid treatment were intact or were gonadectomized on day 2 and given testosterone propionate (TP) treatment on day 7. (It has previously been shown that day 7 is beyond the period of maximum steroid responsiveness in the male but not in the androgenized female.) MER-25, flutamide, or day-2 ovariectomy had no effect on adult marking behavior responsiveness in females given TP on day 7. All groups marked at normal male frequencies. The presence of flutamide prenatally and on the day of birth in day-2 castrates given TP on day 7 yielded adults with marking responsiveness equivalent to day-7 TP-treated females. In contrast, males given day-7 TP without prenatal and birthday flutamide showed significantly lower marking frequencies, suggesting that the presence of androgen prenatally and on the day of birth rendered day-2 castrates less responsive to TP given on day 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment with different antiestrogens in the neonatal period and effects in the cervicovaginal epithelium and ovaries of adult mice: a comparison to estrogen-induced changes

Female mice of the NMRI strain were treated for the first 5 days after birth with the following compounds: diethylstilbestrol (DES), MER-25 (ethamoxytriphetol), tamoxifen, ICI 47.699 (the cis-isomer of tamoxifen, an estrogen agonist), clomiphene, nafoxidine or 17 beta-estradiol-3-benzoate (E2). Females were killed at 8 wk or 6 mo and, in the case of tamoxifen also at 12 mo. The cervicovaginal region and the ovaries were prepared for histological studies. MER-25 had no effect on either the cervicovaginal epithelium or ovarian histology. Tamoxifen, clomiphene and nafoxidine resulted in extensive regions with a heterotopic columnar epithelium (HCE) in the cervicovaginal preparations. At 8 wk these regions were more widespread than those observed after treatment with DES and E2. While earlier studies have shown a progressive development of DES-induced HCE, that induced by the antiestrogens regressed with time. All ovaries from adult females treated with DES or E2 lacked corpora lutea. For the antiestrogens there were ovaries with or without corpora lutea, and this treatment was not incompatible with fertile females. It is concluded that in the neonatal period, the cervicovaginal epithelium is more sensitive to antiestrogens than central structures (hypothalamic nuclei), but for DES the opposite is true.

Effect of the antiestrogen ethamoxytriphetol (MER-25) and luteectomy on serum progesterone concentrations in pregnant baboons

The present study determined whether the reduction in serum progesterone (P4) concentrations which follows the administration of the antiestrogen ethamoxytriphetol [1-(rho-2-diethylaminoethoxyphenyl)1-phenyl-2-rho-methoxyphenyl ethanol (MER-25)] to pregnant baboons reflects a decline in placental and/or luteal function. Maternal saphenous venous blood was collected at 1- to 4-day intervals between day 70 of gestation and term in pregnant baboons. Four females received no other treatment, and eight females received MER-25 (15 mg/kg BW, orally) daily between day 130 of gestation and term. Four of the MER-25-treated baboons received no other treatment, and four had the corpus luteum of pregnancy surgically excised between days 104 and 118 of gestation. Serum P4 concentrations in the untreated baboons fluctuated, but no significant progressive rise or fall in P4 occurred. Administration of antiestrogen to intact pregnant baboons resulted in a 50% decline (P less than 0.001) in serum P4 concentrations from mean pretreatment values of 7.0-25.1 to 4.2-10.8 ng/ml thereafter. Although removal of the corpus luteum alone had no effect on serum P4, administration of MER-25 to luteectomized females resulted in an 80% decrease (P less than 0.001) in serum P4 concentrations from pretreatment means of 10.6-16.6 to 2.5-3.2 ng/ml thereafter. The results indicate that most or all of the P4 that remained in the peripheral circulation after MER-25 administration to intact pregnant baboons originated from the ovary, primarily the corpus luteum. Thus, the major site of action of antiestrogen in reducing P4 production during baboon pregnancy is on the placenta.

Source and regulation of 17 alpha-hydroxyprogesterone during baboon pregnancy

The present study determined the source and regulation of 17 alpha-hydroxyprogesterone (17-OHP4) during mid-late baboon pregnancy. Serum 17-OHP4 (ng/ml) in 5 untreated baboons increased from low values at mid-late gestation to a mean (+/- SEM) of 0.49 +/- 0.02 during the final 20 days of gestation. Fetectomy of 5 baboons resulted in serum 17-OHP4 concentrations which declined to and remained at baseline. Serum 17-OHP4 concentrations were 5- to 10-fold greater (P less than 0.001) in the uterine, utero-ovarian, and umbilical veins than peripherally. Apparently the fetal adrenal provides precursors for placental 17-OHP4 formation because the fetal adrenal gland develops delta 5-3 beta-hydroxysteroid dehydrogenase only late in gestation, and because the fetal adrenal and not the placenta has the capacity for 17-hydroxylation. Thus, at mid-late gestation the placenta appears to supply a major, and at term the corpus luteum a minor portion of the total 17-OHP4. Administration of the estrogen antagonist ethamoxytriphetol (MER-25, 15 mg/kg BW) to 4 baboons did not affect 17-OHP4 during mid-late gestation, when the placenta was the only source of 17-OHP4. However, MER-25 resulted in serum 17-OHP4 concentrations (ng/ml) at term which were greater (1.08 +/- 0.10, P less than 0.001) than in untreated baboons (0.49 +/- 0.02). Prior removal of the corpus luteum of pregnancy in 4 animals subsequently given MER-25 prevented this rise in 17-OHP4. This suggests that the marked elevation in 17-OHP4 observed near term after MER-25 administration was of luteal origin and that antiestrogen enhanced 17-OHP4 secretion by the corpus luteum.

Influence of anti-oestrogens on gonadotrophin secretion in control and ACTH-infused immature rats

The objective of this study was to determine whether anti-oestrogens (nafoxidine, MER-25) would block the suppressive effects of ACTH on gonadotrophin secretion in immature rats. Female rats were castrated at 25-26 days of age, and an Alzet osmotic minipump containing ACTH (1-24) or saline was implanted in each animal. ACTH was administered at a rate of 1 IU/day by constant infusion. Beginning on the day of surgery, animals were injected daily for 5 days with 0.25, 5 or 25 micrograms/100 g body weight of nafoxidine or 5 mg MER-25 and sacrificed on the sixth day following castration. ACTH lowered serum LH concentrations and increased pituitary LH levels. Serum androstenedione concentrations were more than two times greater in ACTH-infused than in control rats, but serum oestrone levels were not affected. Serum testosterone and oestradiol concentrations in ACTH-infused rats remained below levels of detection. Administration of 0.25 micrograms of nafoxidine prevented the suppressive effects of ACTH on serum LH. Serum levels of LH in these animals were comparable to saline-treated controls (418 +/- 94 vs 443 +/- 73 ng/ml). The two higher doses of nafoxidine and MER-25 were ineffective in suppressing the actions of ACTH on serum LH. MER-25 reduced serum LH values in both controls and ACTH-infused rats. Serum FSH concentrations were not altered by ACTH or nafoxidine treatment. MER-25 elevated pituitary FSH concentrations in both control and ACTH-infused rats.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of estrogen antagonism on progesterone production in early pregnancy in the baboon (Papio cynocephalus)

These studies were designed to investigate the role of estrogen on progesterone production in early pregnancy in the baboon, when the contribution of the corpus luteum and placenta has not been established. Oral administration of the estrogen antagonist MER-25 at two dosage levels (15 and 30 mg/kg/day) to the pregnant baboon from days 35 to 55 after conception results in a decline in peripheral plasma levels of progesterone within a few days and persists for at least 20 days after the termination of treatment with no effect on plasma estradiol levels. The same study was done with the use of a different estrogen antagonist, trioxifene mesylate (5 mg/kg/day), and there was no effect on plasma progesterone, although a transient depression in plasma estradiol was evident. These actions may be due to an inherent estrogenicity of trioxifene. In preliminary studies an effect of these estrogen antagonists on placental size and morphology has been observed. Estrogen deprivation in early pregnancy of the baboon results in a depression in plasma progesterone and indicates a placental requirement for estrogen in progesterone product at this stage of pregnancy.

Effects of estradiol benzoate and MER-25 on ethanol consumption in the ovariectomized rat

Daily injections of estradiol benzoate (EB) administered to ovariectomized rats given continuous access to a 10% ethanol solution, to water, and to laboratory chow led to decreases in ethanol consumption. The suppression was transient; ethanol consumption returned to the level of oil-treated control animals after 14 days despite continued hormone administration. This pattern of change in ethanol consumption closely resembled previously reported effects of EB on food intake. It is proposed that a common mechanism was responsible for EB-induced suppression of both food and ethanol intake. Ethamoxytriphetol, MER-25, which antagonizes many estrogen-dependent effects but which mimics the action of EB on food intake, also led to decreases in ethanol consumption that paralleled those reported for food intake. These behavioral effects of EB and MEr-25 were shown not to be due to altered ethanol metabolism or to result from malaise developing out of an interaction between EB and ethanol. It is thus suggested that voluntary consumption of ethanol by the rat is largely due to its caloric content. The relevance of these results for several recent reports of decreased ethanol intake during pregnancy is discussed.

Deleterious effects of prenatal prednisolone exposure upon morphological and behavioral development of mice

The influence of prenatal exposure to the synthetic glucocorticoid prednisolone (PRED) was examined in female offspring of mice administered the drug on Days 13-18 of pregnancy. The offspring weighed significantly less than control animals at birth and weaning. Animals born of mothers given the highest dosage of the drug (400 microgram) weighed less than controls in adulthood. Fetal exposure to PRED also resulted in morphological masculinization as evidenced by an increase in anogenital distance. In addition to its marked influence, prenatal PRED exposure retarded the attainment of the developmental milestones of eye opening, lifting, walking, and gripping. The effect of PRED upon the fetus is relatively rapid in that a reduction of fetal weight was observed in 13-day-old conceptae 7.5 hr following a maternal injection of PRED. The administration of an antiestrogenic compound (MER-25) concurrently with PRED prevented the reduction in birth weight, thereby suggesting that PRED acts, in part, by its known attenuation of fetoneonatal estrogen-binding protein. And finally, fetal exposure to PRED had virtually no effect upon reproductive competence as assessed by proportion of successful pregnancies, lactation performance, and postpartum fighting behavior. It is concluded that prenatal exposure to PRED markedly affects somatic and muscular/motor development and it may be worthwhile to examine the influence of the drug upon levels of gonadal hormones in an attempt to elucidate the mechanism through which its effects are produced.

Food intake, body weight, and adiposity in female rats: actions and interactions of progestins and antiestrogens

A series of experiments examined the effects of two progestins, progesterone and R 5020, and two nonsteroidal antiestrogens, nafoxidine and MER-25, on body weight and composition in female rats. Both progesterone and R 5020 increased food intake, body weight, and carcass adiposity in ovariectomized (OVX) rats treated with estradiol benzoate (EB), but neither progestin had any effect on these measures in OVX rats not treated with EB. R 5020 was substantially more effective than progesterone on all end points. Nafoxidine and MER-25 mimicked the actions of estradiol and decreased adipose tissue lipoprotein lipase (LPL) activity by 75-80%. For adipose tissue LPL activity, both nafoxidine and MER-25 were full estrogen agonists and without antiestrogenic activity. Nafoxidine also mimicked the effects of EB by reducing food intake, body weight, and carcass adiposity in OVX rats. In contrast, nafoxidine antagonized the induction of cytoplasmic progestin ([3H]R 5020) binding sites by EB in parametrial adipose tissue of OVX rats. In nafoxidine-treated OVX rats, concurrent progesterone administration had no effect on adipose tissue LPL activity, but progesterone did increase food intake, body weight, and carcass fat content. Some physiological mechanisms by which gonadal steroids may act to influence eating and adiposity are discussed.

Effect of estrogen on denervated muscle

The rate of increase of glucose 6-phosphate dehydrogenase activity in denervated rat extensor digitorum longus muscle shows sexual dimorphism. This phenomenon is further investigated in this report by assessing the effects of ovariectomy, hypophysectomy, hormone replacement therapy, and treatment with an estrogen antagonist , MER-25. The data demonstrate that physiologic doses of estrogens enhance the rate and extent of the increase in glucose 6-phosphate dehydrogenase activity after denervation. The data further indicate that aromatization of androgens may be a significant source of estrogen involved in hormonal modulation of the neural control of glucose 6-phosphate dehydrogenase and other processes in muscle. Furthermore, choline acetyltransferase activity, a marker for the neuromuscular synapse, decreased in rat extensor digitorum longus muscles after denervation, but was unaffected by ovariectomy.

Suprachiasmatic lesions disrupt the daily rhythmicity in the sexual behaviour of normal male rats and of male rats treated neonatally with antioestrogen

Male rats were treated daily with oil or 100 micrograms of the antioestrogen, ethamoxytriphetol (MER-25), for the first 10 days of life and, when adult, lesions were made in the suprachiasmatic nuclei (SCN) of the hypothalamus or control lesions were made above the SCN and the rats were tested for sexual behaviour. Treatment with MER-25 enhanced the daily rhythmicity in both mounting and lordosis behaviour and SCN lesions disrupted these behavioural rhythms and the rhythm in the mounting behaviour of oil-treated rats. Rats treated with MER-25 and with SCN lesions showed high levels of mounting and lordosis behaviour throughout the light : darkness cycle. These results support the hypothesis that sexual differentiation by perinatal androgen stimulation uncouples the central rhythm generator from the neural substrates of sexual behaviour in rats.

Neonatal treatment with antioestrogen increases the diurnal rhythmicity in the sexual behaviour of adult male rats

Male rats were given daily injections of the antioestrogen ethamoxytriphetol (MER-25, 100 microgram/day) or oil during the first 10 days of life. Rats treated with MER-25 showed a more pronounced diurnal rhythm in both mounting behaviour and lordosis behaviour than did oil-treated rats when tested as intact adults and after castration together with treatment with testosterone- or oestradiol-filled constant release implants. Serum levels of androgen varied markedly in samples obtained at four different times of the light : darkness (LD) cycle in both neonatal treatment groups and no significant LD-dependent pattern was obvious. Castration and treatment with testosterone implants produced stable androgen levels which showed little individual variation and did not vary with the LD cycle. The results supported the hypothesis that perinatal androgen stimulation affects the development of sexual behaviour in rats primarily by decreasing the diurnal rhythmicity of the behaviour of the adult.

A role for estrogen in progesterone production during baboon pregnancy

The present study determined whether estrogen is important in the production of progesterone (P) during primate pregnancy. Serum P production rates (metabolic clearance rate [MCR] x peripheral serum concentration) were determined in baboons prior to and following maternal administration of the antiestrogen ethamoxytriphetol (MER-25) at 30, 15, 6, or 3 mg/kg of body weight by mouth daily for 10 or 20 day periods during or throughout the last one third of gestation. Maternal peripheral serum P concentrations decreased (p less than 0.05 to P less than 0.001, t test) 37 to 60% in 7 of 9 baboons following daily administration of MER-25. Since mean MCR-P prior to (1,567 1/day) and following (1,361 1/day) MER-25 were similar, the decline in serum P concentration reflected decreased P production. Serum P concentrations in five untreated baboons during the last one third of gestation fluctuated in level, but no significant sequential rise or fall occurred. The decrease in P production in baboons following antiestrogen administration suggests that the action of estrogen is required for sustaining the elevated P production typical of baboon pregnancy.

Differential depletion of cytoplasmic high affinity oestrogen receptors after the in vivo administration of the antioestrogens, clomiphene, MER-25 and tamoxifen

1 The in vivo actions of the oestrogen antagonists, MER-25 and tamoxifen upon the cytosol oestrogen receptors prepared from amygdala, hypothalamus, pituitary and uterus of rats were studied 24 h after drug administration. 2 There was a dose-related depletion of cytosol oestrogen receptors. However, the uterine and pituitary receptors were consistently affected at a lower dose than were those from the brain. 3 The ratios of the combined central ED50 to the combined peripheral ED50 were clomiphene 169 greater than MER-25 19.2 greater than tamoxifen 2.13. 4 The receptor changes were not related to biological activity monitored by serum luteinizing hormone levels and uterotrophic response. 5 The possible role of these drug effects in the induction of ovulation and future developments are discussed.

Lordosis behaviour in immature male rats

Lordosis behaviour was induced in immature 20-day-old male rats by sequential treatment with oestradiol benzoate (OB) and progesterone, but prepubertal male rats were behaviourally less sensitive to the OB and progesterone treatment than were female rats. Thus, the sex difference in the lordosis response was present early during development. Castration at various times after birth showed that the capacity of immature rats to show lordosis is normally inhibited by an action of testicular secretions exerted during the first 10 days of life. Treatment of day 0 castrated rats with OB, either as a single injection given on the day of birth or as daily injections given on the first 10 days after birth, was much more effective in inhibiting the display of lordosis behaviour at 30 and 37 days of age than was treatment with testosterone benzoate (TB). Treatment with dihydrotestosterone benzoate neonatally had no inhibitory effect. Treatment of intact male rats or day 0 castrated OB-or TB-treated rats with the anti-oestrogen ethamoxytriphetol (MER-25) during the first 10 days of life antagonized the inhibitory effect of the testes and of the OB or TB treatment on the development of the lordosis response. It is suggested that during normal development oestradiol formed in the brain from testosterone in the circulation acts during the first 10 days of life to inhibit the capacity of male rats to show lordosis when adult.

Effects of anti-oestrogen treatment of neonatal male rats on lordosis behaviour and mounting behaviour in the adult

Male rats were treated daily with 100 microgram of the anti-oestrogen ethamoxytriphetol (MER-25) or oil during the first 10 days of life and tested for lordosis behaviour and mounting behaviour as intact adults, after castration and after castration and oestradiol benzoate or testosterone propionate treatment. The MER-25-treated rats showed higher levels of lordosis behaviour than oil-treated rats in all four treatment groups. Under each of these endocrine conditions, except after castration alone, the MER-25-treated rats showed a reduced capacity to ejaculate. Treatment of the neonatal rat with MER-25 reduced body weight in adulthood but did not change the weight of the accessory sexual glands, the testes, the number of cornified papillae on the glans penis or plasma testosterone concentrations during development. The response of the accessory sexual glands and cornified papillae on the glans penis to treatment with oestradiol benzoate or testosterone propionate after castration in adulthood was unaffected by treatment with MER-25. It is suggested that formation of oestrogen in the neonatal male rat brain from testosterone in the circulation inhibits the capacity to show lordosis behaviour and facilitates the capacity to ejaculate in response to ejaculate in response to gonadal hormone treatment in adulthood.

Sexual behaviour of male rats injected with the anti-oestrogen MER-25 during infancy

Newborn male rats were injected SC with 50, 100 or 200 micrograms MER-25 or 0.05 ml oil daily for the first 10 days of life. As adults, they were tested for male sexual behaviour both before and after castration and replacement with testosterone propionate, and for female sexual behaviour after injections of oestradiol benzoate followed by progesterone. Injections of 100 and 200 micrograms MER-25/day during infancy caused significantly fewer rats to ejaculate than 0.05 ml oil/day in both series of tests for male sexual behaviour. The reduced occurrence of ejaculation could not be related to defective penile development as there was no significant difference in penis weights or the numbers of penile spines between the MER-25 and oil-injected rats. All doses of MER-25 caused significantly more lordosis behaviour after oestrogen and progesterone than did injections of oil. These results provide further evidence that neonatal testicular androgens must be converted to oestrogen in the brain in order to organise male sexual behaviour patterns, including the neural substrate for ejaculation, as well as to suppress female sexual behaviour.

Binding of [3-H]estradiol by brain cell nuclei and female rat sexual behavior: inhibition by antiestrogens

The antiestrogens MER-25, CI-628, and nafoxidine inhibit the uptake of [3H]-estradiol in whole homogenates and isolated cell nuclei tissues and the pituitary, and inhibit estradiol-induced female sexual behavior. The antiestrogens were injected intraperitoneally 2 h prior to an intravenous injection of [3H]estradiol, and the animals were killed 2 h after the estradiol. CI-628 reduces radioactivity in whole homogenates and isolated cell nuclei of cerebral cortex, hypothalamus, preoptic area -septum and pituitary. Nafoxidine reduces uptake in cell nuclei of the hypothalamus, preoptic area-septum and pituitary. In this paradigm, MER-25 inhibited uptake only in the pituitary. In the analogous behavioral experiments, with antiestrogens injected 2 h prior to an intravenous injection of unesterified estradiol, CI-628 and nafoxidine totally inhibited lordosis responding. MER-25 shows no inhibition of behavior in this paradigm. However, when MER-25 is injected 12 h prior to the estradiol, it inhibits retention of [3H]estradiol at 2 h in brain and pituitary cell nuclei, and lordosis responding is also inhibited. Additionally, the antiestrogens can apparently displace previously bound [3H]estrdiol. When the antiestrogens are injected 2 h prior to an injection of [3H]estradiol, MER-25, CI-628 and nafoxidine all show greater inhibition of nuclear estradiol retention at 12 h after the [3H]estradiol injection than 2 h. Analogously, when CI-628 is injected 2 h after an intravenous injection of [3H]estradiol, it displaces most of the radioactivity present in hypothalamic-preoptic area nuclei at 12 h after the estradiol injection. These results indicate that antiestrogens can prevent or reverse the nuclear concentration of estradiol in brain cells and are consistent with a role of the cell nucleus in the induction of estrous behavior by estradiol.

Oestrogenic, anti-oestrogenic and fertility effects of some triphenylethanes and triphenylethylenes related to ethamoxytriphetol (MER 25)

Five triphenylethylenes, a triphenylethane and a triphenylethanol, carrying methyl substituents ortho to one or both of the ring oxygen functions, have been examined for oestrogenic, and antioestrogenic activity in mice, and three of the compounds, alpha-[4-(beta-diethylaminoethoxy)-3, 5-xylyl]-alpha-phenyl-beta-4-methoxyphenyl-ethanol (IV), alpha'-[4-(beta-diethylaminoethoxy)-3, 5-xylyl]-4-methoxy-bibenzyl (V) and alpha'-[4-(beta-diethylaminoethoxy)-3, 5-xylyl]-4-methoxy-stilbene (VI), were tested for their effects on fertility in mice. 2 Orthomethylation reduces oestrogenic and/or anti-oestrogenic activity compared with the reported activities of non-methylated analogues. 3 The anti-oestrogenic ethamoxytriphetol (MER 25) reduced fertility in mice whereas its inactive dimethylated analogue (IV) was ineffective. The weakly active anti-oestrogens, V and VI, did not affect fertility in mice.

Considerations into the mechanism of estrogen-stimulated uterine prostaglandin synthesis

Progesterone priming of the ovariectomized rat, followed by a single injection of estradiol-17beta (10 mug) is followed by an increased uterine synthesis of both PGF and PGE. The administration of an estrogen antagonist (MER-25; 10 mg) concomitantly with estradiol had no effect on uterine prostaglandin synthesis. Similarly, the administration of either Actinomycin D or cycloheximide, antibiotics demonstrated to inhibit mRNA and protein synthesis, respectively, is without effect on estrogen-stimulated uterine prostaglandin synthesis. These results are considered with regard to the classic receptor theory of estrogen action and are a preliminary indication that estrogen-stimulated uterine prostaglandin synthesis may not require those receptor mediated events.