Uterine Weight Response Research Articles

Comparative effects of estradiol, raloxifene, and genistein on the uterus of ovariectomized mice

To explore the uterine effects of administration of compounds that exert their bone-sparing functions through estrogen receptors, we administered 17beta-E2, raloxifene, or genistein to ovariectomized mice and analyzed the uterus weight and histology 4 weeks after beginning the treatments. Results indicated that raloxifene and genistein have partial agonistic properties on the uterus in estrogen-depleted mice, and that genistein induced apoptosis and several atypias in the glandular epithelium of endometrium, as demonstrated in hematoxylin-eosin-stained histological sections.

Acute and permanent growth effects in the mouse uterus after neonatal treatment with estrogens

Acute and late effects of neonatal estrogen treatment were studied in NMRI mice treated with diethylstilbestrol (DES) or estradiol-17β (E 2) on days 1 to 5 after birth (estrogenized females). The uterine wet weight (UWW) response in 6-day-old females, after 5 daily treatments with DES, had a peak at a daily dose of 10 −2 μg DES and declined with higher doses. Females (26-day-old) treated with DES or E 2 neonatally had a reduced UWW response to a challenge with DES; on a dose basis, DES was more effective neonatally than E 2. A single injection with DES or E 2 in the neonatal period stimulated mitotic activity in the uterine horn epithelium; the UWW response to a 24-h DES pulse increased from day 2 to 6 after birth, but the uterine epithelial mitotic rate response decreased. Epidermal growth factor (EGF) was a more potent stimulator of mitotic activity than DES or E 2. DES inhibited mitotic activity in the uterine cervical epithelium; EGF protected from this DES effect. In adult estrogenized females; EGF-induced uterine stimulation of 3H-thymidine incorporation subsided more rapidly than in control females; uterine epithelium did not respond to EGF in vitro. Uterine stroma of adult estrogenized females is postulated to house a population of cells under nonovarian proliferation control while the uterine epithelium may be under influence of an ovary-dependent proliferation inhibiting factor that is gradually lost under culture conditions.

Δ 9-Tetrahydrocannabinol antagonism of the anterior pituitary response to estradiol in immature female rats

The potential estrogenicity or antiestrogenicity of Δ 9-tetrahydrocannabinol (THC), the chief psychoactive constituent of marijuana, was evaluated in immature female rats treated for 3 days with estradiol (E 2; 1 μg/kg), THC (10 mg/kg body weight), or E 2 + THC. Estradiol treatment significantly increased anterior pituitary, uterine, and oviduct weights. When THC was administered with E 2, it prevented the E 2-induced increase in pituitary weight, but had no effect on either the uterine or oviduct weight response to E 2. In the E 2 treatment group, basal prolactin levels were increased and a prolactin surge occurred on the afternoon of the 26th day of age. However, E 2-stimulated basal and surge levels of prolactin were significantly attenuated by concomitant THC treatment. Moreover, pituitary prolactin concentrations, which were elevated in Entreated rats, did not differ from control values in E 2 + THC-treated animals. The E 2-induced decrease in dopamine turnover rates in the medial basal hypothalamus and increase in the number of anterior pituitary dopamine D 2-binding sites (B max) were not affected by concomitant THC treatment. Thus, THC antagonizes E 2 action on the anterior pituitary via yet to be elucidated mechanism(s).

Effect of lindane on hormonal control of reproductive function in the female rat

The effect of the γ isomer of 1,2,3,4,5,6-hexachlorocyclohexane, lindane, on reproductive function in the female rat was examined in two experiments. In the first experiment, chronic treatment with 0, 5, 10, 20, and 40 mg/kg lindane delayed vaginal opening and disrupted ovarian cyclicity until approximately 110 days of age. Thereafter, regular ovarian cycles were present in the majority of females in all dose groups. When killed on the day of vaginal proestrus, the females receiving the two higher doses of lindane had smaller pituitary and uterine weights, lower serum and pituitary luteinizing hormone (LH) and prolactin, and higher pituitary follicle stimulating hormone (FSH) concentrations that the oil-treated control females. Serum estrogen concentrations were not different from controls in the 5 and 20 mg/kg groups, significantly greater than the controls in the 10 mg/kg group, and significantly less than the controls in the group receiving 40 mg/kg. In a second experiment, the uterine weight and pituitary hormone response of 28-day-old, lindane-treated females to a 10-μg injection of estradiol benzoate (EB) were investigated. The uteri of the lindane-treated prepubertal females were smaller than controls at 30 hr after EB injection. Furthermore, the EB-induced increase in serum luteinizing hormone, observed at 30 hr after EB injection, was lower in the lindane-treated animals. Similarly, the reduction in pituitary LH, FSH, and prolactin induced by EB was not as great in the lindane-treated animals as in the controls. Serum estrogen concentrations in the lindane-treated animals were not different from controls. These data indicate that lindane may effectively block the response of estrogen-dependent tissues to this ovarian steroid hormone and that this apparent antiestrogenic effect of lindane is responsible for the disturbances observed in the neuroendocrine control of ovarian function in the rat.

Binding and biologic activity of diethylstilbestrol in the hamster: Influence of a serum component on estrogen receptor binding and estrogenic activity

The purpose of this study was to compare the biological activity and estrogen receptor (Re) binding affinity of diethylstilbestrol (DES) and estradiol (E 2). Uterine weight response and cytosolic progesterone receptor (Rp) induction were equivalent following daily (3 days) injections of DES or E 2 to ovariectomized animals. The biological equivalence of DES and E 2 was not reflected by competition assays done with either uterine cytosolic or nuclear Re: the relative binding affinity (RBA) of DES to cytosolic Re was 46 ± 5.3 and to nuclear Re was 380 ± 42 compared to E 2 (100). The RBAs of estrone, estriol and enclomiphene with cytosolic or nuclear Re were not significantly different. Further studies showed that this discrepancy in RBA of DES between cytosolic and nuclear Re could not be attributed to salt concentration but could be mimicked by addition of serum to nuclear Re preparations. The RBA of DES done with ammonium sulfate precipitated cytosolic Re approached that observed for nuclear Re. Gel filtration chromatography (Sephacryl S-300) of serum bound tritiated DES was shown to coelute with bovine serum albumin. These results suggest that a serum component (tentatively identified as albumin) can bind DES and cause a decrease in in vitro binding affinity and a reduction in biological activity in vivo.

Effects of purified (AIN‐76A) and natural‐ingredient (NIH‐07) diets on responses of BALB/c and B6C3F1female mice to estradiol

Female BALB/c and B6C3F1 mice were examined after a 3-wk exposure to dietary estradiol (0, 400, 800, 1600, and 3200 ppb) in a purified (AIN-76A) or a natural-ingredient (NIH-07) diet. The use of AIN-76A was associated with a 9-13% greater (p less than 0.001) body weight and a 36-43% higher (p less than 0.001) serum cholesterol in both mouse genotypes when compared to mice fed NIH-07. Conversely, when fed NIH-07, both mouse genotypes had a 20-22% higher (p less than 0.003) serum urea nitogren and 2-3.5% higher erythrocyte count (p less than 0.001) and hemoglobin concentration (p less than 0.04) than when fed AIN-76A. Reduced erythrocyte parameters suggest that chronic feeding of the purified diet might result in anemia. No significant compound or diet-related differences were noted for serum creatinine, alanine aminotransferase, aspartate aminotransferase, or gamma-glutamyl transferase. Although there was no diet effect on absolute or differential white blood cell count, estradiol caused a decrease in the total white blood cell count (p less than 0.014) and an increase in the percentage of polymorphonuclear leukocytes (p less than 0.014) in BALB/c and decreased the percentage of lymphocytes (p less than 0.005) in B6C3F1 females. In addition, estradiol increased uterine weight and inhibited thymic and splenic weights in one or both genotypes. Spleen and thymus weight responses to estradiol were not significantly influenced by diet. However, the uterine weight responses to estradiol were apparently influenced by diet in both genotypes. In B6C3F1 mice, the uterus weighed more at each level of estradiol when mice were fed AIN-76A compared to NIH-07 diet. In BALB/c mice, this was true only at the two lower dietary concentrations of estradiol. In conclusion, mice fed the purified diet, AIN-76A, differed from those fed the cereal-based diet, NIH-07, in hematology, clinical chemistry, and uterine weight response to estradiol.

Inhibition of sexual receptivity by anesthesia during estrogen priming

Anesthetics such as pentobarbital have been used to infer a role of neural activity in several neuroendocrine responses. The present experiments tested the hypothesis that neural activity during estrogen priming is necessary for the induction of sexual receptivity. Sexual behavior was induced in overiectomized female rats by tow pulses of unesterified estradiol 6 h apart, followed by progesterone at 19 h and testing at 24 h. Anesthetizing animals for approximately 1 h during each exposure to estradiol inhibited the induction of receptivity. Anesthesia immediately before each exposure to estradiol did not interfere with the induction of sexual receptivity. The induction of neural progestin receptors by estradiol was not prevented by anesthesia. Anesthesia had no effect on the uterine weight response to estradiol. These results suggest that neural activity during estrogen priming is required for the induction of sexual receptivity, and point to differences in the mechanism of action of estrogens in the brain and the uterus.

Characterization of uterine growth response to cholera toxin in hamsters and test of heat-labile enterotoxin from Escherichia coli.

Cholera toxin (CT) and the heat-labile enterotoxin from Escherichia coli, when injected intraperitoneally into cycling hamsters but not rats or mice, induced a massive uterine growth similar to that normally induced by the implanting blastocyst during pregnancy. CT and heat-labile enterotoxin are the only known agents that have this action in any species. Uterine weight reached a maximal sixfold increase 48 h after injection of CT. Concurrent injection of estrogen, progesterone, and CT increased the maximal response to eightfold and eliminated differences in the response to CT injected on different days of the 4-day hamster estrous cycle. The dose response for CT, heat-labile enterotoxin, and CT plus estrogen plus progesterone was most linear (r greater than 0.93) when the logarithm of uterine weight was plotted against the dose of toxin. The hamster uterine weight response can serve as a simple, highly precise, and highly specific bioassay for CT and heat-labile enterotoxin.

Anti-oestrogen modification of uterine responses to oestrogen in the rat.

Oestradiol (single injection) resulted in a peak in uterine blood flow 3 h later with a secondary rise in blood flow at 30 h. Uterine wet and dry weights increased more slowly and were still above control values 24 h after the injection. If a second injection of oestradiol was given 24 h after the first then uterine blood flow was again maximal at 3 h but remained at this level for a further 3 h, probably due to the secondary rise induced by the first injection. Uterine wet weight was further increased by the second injection of oestradiol but the effect did not occur until 6 h after the oestrogen treatment. Pretreatment with an anti-oestrogen, tamoxifen or nafoxidine, inhibited or reduced significantly the uterine weight and uterine blood flow responses to oestrogen but increased uterine weights and produced some increase in uterine blood flow when given alone. It is suggested that both blood flow and weight responses to oestrogen in the uterus are mediated through the oestrogen receptors.

Combined treatment with radioestradiol-lucanthone in mouse C3HBA mammary adenocarcinoma and with estradiol-lucanthone in an estrogen bioassay

C3H female mice bearing transplantable estrogen-nondependent adenocarcinomas were treated subcutaneously with either estradiol, tritiated ( 3H)estradiol, lucanthone, 3H-estradiol followed by lucanthone, or lucanthone followed by 3H-estradiol. Tumor growth and host survival were ascertained. As single agents, lucanthone or 3H-estradiol had slight tutor-inhibiting effects with small tumors. Combined treatment with radioestrogen followed by htcatlthone 4 hrs later blocked early tumor growth for several days and permanently reduced the growth rate thereafter; it also lengthened survival by some 67%. On the other hand, combined treatment with lucanthone followed 1 hr later by 3H-estradiol did not have the same effect. The increase in adrenal gland weight that occurs as this tumor grows was significantly reduced by treatment with lucanthone, and more so by 3HE2…..+Lu; both of these treatmelnts also depressed the lymphatic system. It is suggested that the antitumor effects observed may be mediated-systemically via the adrenal. None of the treatments were effective against advanced tumors. Lucantbone was also administered subcutaneously to w female Swiss mice in conjunction with estradiol. Evidence showed that lucanthone interferes with the immature mouse uterine weight response to estrogen, especially what given 1 hr before the hormone. Although an estrogen dose-response relationship was demonstrated for all groups, the hormone and the DNA intercalating agent interfered with each other in a way that suggests possiblle steric or competitive inhibition. Thus lucanthone modulates two estrogen effects, namely, the effect of estrogen out an estrogen-response tissue (uterine weight, especially when given prior to the hormone), and the effect of radioestrogen on an estrogen-nondependent antonomous tumor (when given after the hormone). A novel antitumor strategy, here called radiocytochemotherapy, is described, and possible applications to human tumors are discussed.

III. HORMONAL SPECTRA OF ANTI-ANDROGEN TSAA-291 (16β-ETHYL-17β-HYDROXY-4-OESTREN-3-ONE) AND ITS DERIVATIVES

For the purpose of obtaining hormonal spectra of anti-androgen TSAA-291 and its derivatives, a variety of endocrine characteristics were studied. (1) Androgenic and anabolic activity : Subcutaneous administration of anti-androgen TSAA-291 and its acetate, TSAA-328, to the immature orchiectomized rat resulted in significant weight increase of the levator ani but in only a nominal response of seminal vesicles and prostates even at a large daily dose of 9.6 mg. The resultant anabolic/androgenic ratio was estimated to be extremely high. (2) Oestrogenic activity : Uterine weight in response to these anti-androgens were sluggishly dose-dependent, and the maximal plateau response remained considerably lower than that induced by oestradiol-17 beta. The oestrogenic activity of these anti-androgens was estimated to be 1/200 000 or less as that of oestradiol-17 beta. A single subcutaneous dose of 100 mg of TSAA-291 or its caproate, TSAA-330, did not induce the vaginal cornification in the adult ovariectomized rat. (3) Anti-oestrogenic activity : Antagonistic effect of these anti-androgenic compounds on the uterine weight response to oestradiol-17 beta was found in the immature ovariectomized rat. A single subcutaneous dose of 100 mg of TSAA-291 or TSAA-330 also induced the antagonism against the cornification caused by daily treatments with 1 microgram oestrone in the adult ovariectomized rat. (4) Progestational activity : These anti-androgenic compounds proved to be less active than progesterone in the McPhail's test. (5) Anti-inflammatory activity : Daily subcutaneous dose of 20 mg of TSAA-291 for 6 days did not significantly depress the weight of granuloma developed around the cotton-pellet implanted in the young male rat. TSAA-291 did not affect the anti-inflammatory action of 1/6 mg of prednisolone phosphate. Combination of both agents seemed to be effective in enhancing the anti-androgenic action of TSAA-291, whereas prednisolone phosphate alone rather increased the weight of the accessory sex organs. (6) Liver glycogen deposition activity : Daily intramuscular doses up to 38.4 mg of TSAA-291 for 5 days did not increase the liver glycogen level in the adrenalectomized rat.

Variability of response to diethylstilbestrol: A comparison of inbred with hybrid mice

The uterine and thymic weight responses to diethylstilbestrol (DES) were examined in BALB/cStCrlfC3Hf/Nctr, C57BL/6JfC3Hf/Nctr, C57BL/6 × BALB/c F 1 hybrid (F1), and monohybrid cross offspring (F2) from the breeding of F 1 mice. Weanling females were exposed for 6 d to dietary concentrations of DES of 2.5–1000 ppb (μg/kg feed). About 400 mice of each genetic population were used. In the uterine weight assay the slope of the dose‐response line was significantly less for the BALB/c than for the other populations. Uterine weight variances for the F 1 hybrid and BALB/c mice were indistinguishable from each other and significantly smaller than variances for the F 2 hybrid and C57BL/6 mice. Similarly, thymic weight variances were smallest for BALB/c and F 1 mice and highest for C57BL/6 mice. In other studies the body weight responses were examined and gross necropsy observations were recorded for pituitaries and testes during a chronic feeding study with dietary concentrations of DES of 5–640 ppb. A total of 57...

Estrogen Binding in Mammary Tissue of C3H Mice With or Without the Mouse Mammary Tumor Virus

Substrains of C3H mice, with and without the milk-transmitted form of the mouse mammary tumor virus (MMTV)1, were compared to determine if the presence of MMTV altered estrogen action. Uterine weight response to oral diethylstilbestrol was the same for both substrains, (MMTV+ and MMTV-). The concentration of high-affinity estrogen binding sites ("receptors") in lactating mammary tissue did not differ significantly for MMTV+ versus MMTV- mice; the affinity of the estradiol-receptor interaction appeared higher, however, in cytosol from MMTV- mice. Sucrose density gradient analysis revealed no significant differences in sedimentation properties of cytosol receptor from the two substrains.

ChemInform Abstract: POTENTIAL STEROIDAL ANTIESTROGENS

AbstractDurch Oxidation von (I) bzw. (III) entstehen die 6‐Oxo‐estradiole (II), die mit Phenylmagnesiumbromid zu den 6‐Phenyl‐Verbindungen (IV) umgesetzt werden.

Strain differences in the response of the mouse to diethylstilbestrol.

BALB/c StCrlfC3Hf/Nctr, C57BL/6/, C57BL/6 X BALB/c F1 hybrid (B6CF1), and monohybrid-cross offspring from the breeding of B6CF1 mice were examined with respect to uterine, vaginal, and thymus responses to diethylstilbestrol (DES). About 400 mice of each genetic population were used. Weanling mice were fed DES at dietary concentrations of 2.5 to 1,000 ppb (microgram/kg feed) for 6 days and were killed by cervical dislocation about 20 hr after removal of the feed. C57BL/6, B6CF1, and the monohybrid-cross offspring did not differ in the uterine-weight response to DES, but the slope of the dose-response line was shallower for the BALB/c than for the other strains. Dietary DES concentrations of 250 ppb or more inhibited the uterotrophic response in all populations. Vaginal cornification occurred at lower concentrations of DES in the C57BL/6 strain than in the B6CF1 animals. BALB/c and monohybrid-cross offspring were indistinguishable from each other in their vaginal response to Des and were less sensitive to DES than the other mouse populations. The use of ethanol or corn oil as the solvent for mixing DES into the diet had no apparent effect on the uterine weight or vaginal response in any of the mice. DES depressed thymus weight in a dose-related fashion at dietary concentrations of 100 ppb and above in all genetic populations.

Potential steroidal antiestrogens.

A series of analogues of 17beta-estradiol has been synthesized and the compounds have been tested, using sucrose density gradient analysis, for their ability to compete with [6,7-3H]-17beta-estradiol for the estrogen-receptor protein from mouse uterine homogenates. Active compounds were also tested for antiuterotrophic activity in immature rats and/or mice. 3,17beta-Dihydroxy-6-phenylestra-1,3,5(10),6-tetraene (14) was the most active new compound in the in vitro test suppressing the binding of 17beta-estradiol by 34 and 87%, respectively, at molar ratios of 1 and 3.16. It was significantly more potent than the intermediate 6-oxoestradiol (4) which produced a 52% inhibition of binding at a molar ratio of 3.16. The thiosemicarbazone of 6-oxoestradiol (17) and the derived 3,17beta-dihydroxy-6-(2-imino-4-oxothiazolidinyl-1-imino)estra-1,3,5(10)-triene (19) produced, respectively, only 46 and 16% inhibition of binding at a molar ratio of 10. Introduction of a 1-methyl substituent into either 6-oxo or 6-phenyl compounds reduced affinity for the receptor significantly (compounds 5 and 15) and conversion of the 3-OH into a beta-dialkylaminoethoxy group virtually destroyed all binding activity (compounds 2, 6, 10, and 11). At a molar ratio of 10 compound 14 failed to suppress the uterine weight response of immature rats to 17beta-estradiol, whereas compound 15, at a molar ratio of 200, produced a significant increase in the uterine weight of immature rats but not of immature mice even at a molar ratio of 1000.

Stimulation of aromatization of exogenous and endogenous androgens in ovaries of hypophysectomized rats in vivo by follicle-stimulating hormone.

The role of follicle-stimulating hormone (FSH) in the regulation of estrogen biosynthesis in vivo has been investigated in immature hypophysectomized rats, utilizing uterine weight and histologic responses, and ovarian estradiol-17beta concentrations as indicators of estrogen secretion. A highly purified FSH preparation produced only borderline increases in uterine weights and in ovarian estradiol-17beta contents when administered alone at 2.5 mug/day for 3 days. Testosterone or androstenedione (5 mg/day), when administered in the absence of FSH, produced typically androgenic stimulation of uteri, and did not increase ovarian estradiol-17beta concentrations. When administered concomitantly with FSH, the uterine weight-stimulating activity of these aromatizable androgens was substantially increased, accompanied by marked hypertrophy of the endometrial mucosal cells, and ovarian estradiol-17beta concentrations were increased 20- to 200-fold. The administration of the non-aromatizable androgen, 17beta-OH-5alpha-androstan-3-one (DHT) (5 mg/day, by itself produced uterine weight increases similar to those caused by testosterone alone; however, no evidence of increased estrogen secretion resulted from the combined treatment of DHT wtih FSH. A highly purified luteinizing hormone (LH) preparation was equally as effective as exogenous androstenedione in increasing ovarian concentrations of immunoreactive androgen (testosterone + DHT) but evoked none of the above signs of estrogen secretion unless administered together with FSH. The weights of ovaries were not affected by the administration of LH or of any of the androgens by themselves, but were approximately doubled by FSH alone. Ovarian weights were increased still further when FSH was administered concomitantly with LH, testosterone , or androstenedione, but not with DHT. It is concluded that FSH and LH regulate ovarian estrogen secretion in vivo by acting at biochemically distinct sites--LH stimulating the synthesis of C19-steroids, which are then converted to estradiol-17beta under specific stimulation by FSH.

New Concepts on the Action of Oestrogens in the Uterus and the Role of the Eosinophil Receptor System

Two receptor systems for oestrogens have been demonstrated in the uterus: the cytosol-nuclear receptor system and the eosinophil receptor system. It has been proposed that the cytosol-nuclear receptor system mediates the genomic response to oestrogens in the uterus, while the eosinophil receptor system is thought to mediate the uterine edema and other early oestrogenic responses in the uterus. Cortisol is known to decrease drastically the number of eosinophils in the blood and therefore to limit their availability for migration to the uterus. The present results show that cortisol also drastically reduces both the oestrogen-induced uterine eosinophilia and the uterine wet weight responses, but does not interfere with the oestrogen-induced uterine RNA and protein increases. Oestradiol-17 beta has a higher affinity than oestriol for the cytosol-nuclear receptors and is now found to be the more potent oestrogen in inducing the genomic activation in the uterus. Estriol has a higher affinity than oestradiol-17 beta for the eosinophil receptors, and therefore, oestriol is the stronger oestrogen in inducing those oestrogenic effects which are mediated by the eosinophil receptor system. We conclude that the eosinophil receptor system for oestrogens is a new system, independent of Jensen's cytosol-nuclear receptor system, and this eosinophil receptor system is involved in the mechanism of oestrogen action in the uterus.

Effects of postnatal thyroxine administration on brain development, response to postnatal androgen and thyroid regulation in female rats.

Some developmental and functional manifestations of thyroxine (T4) administered on the first 2 days of postnatal life were studied in the female rat. Brain myelinogenesis estimated by brain esterified cholesterol concentration, and brain myelin age estimated by brain total cholesterol concentration, were subsequently determined. Thyroxine treatment resulted in a greater concentration of esterified cholesterol in the brain that saline treatment, but the latter appeared to delay the normal increase shown by non-injected controls. Thyroxine treatment resulted in total and free cholesterol levels similar to those of non-injected controls, these again being greater than those in saline-treated rats. Cholesterol concentrations in liver and serum were not affected by T4 or saline treatment. Administration of T4 to female rats before administration of 1-25 mg testosterone propionate on day 7 resulted in an ovarian and uterine weight response to human chorionic gonadotrophin (HCG, 1 i.u./day on days 23-26) on day 27 that was greater than that in litter-mates given saline at birth before testosterone propionate and HCG treatment. Postnatal T4 treatment alone in the female was also associated with a reduced thyroid and pituitary gland enlargement after 7 days of propylthiouracil feeding (0-015% in tap water, days 24-31 of life) when compared with either saline or non-injected controls.

Interactions between phyto-oestrogens and steroids in the cervical mucus and uterine weight responses in ewes

Cervical mucus and uterine weight responses were measured in ovariectomized ewes grazing pastures containing isoflavones and coumestans—red clover (Trifolium pyatense) and lucerne (Medicago sativa) respectively. The red clover pastures were highly oestrogenic to the ewes, large productions of mucus and high uterine weights being recorded. Grazing of these pastures for a 12-day period prior to bioassay had no significant effect on either response. The lucerne pastures were only mildly oestrogenic. Administration of progesterone either by subcutaneous implant (375 mg progesterone) or intramuscular injection (10 mg per ewe per day) inhibited the mucus responses to isoflavones but did not decrease the uterine weight responses. In one of two experiments, the uterine weight was unaffected and in the other experiment the weight was enhanced by progesterone treatment. Testosterone propionate injections (10 mg per ewe per day) had no effect on either the cervical mucus or uterine weight responses, but induced oestrus in all ewes.