Steroid receptors and effects of oestradiol and progesterone on chick oviduct proteins

After a single injection of oestradiol benzoate (1.5 mg/kg) to oestrogen-withdrawn chickens, there was an increase in magnum wet weight, DNA polymerase alpha activity, adenosine-3',5'-monophosphate-dependent protein-kinase activity and estrogen-receptor concentration, as measured over 36 h. Besides these intracellular proteins, the secretory proteins ovalbumin and conalbumin were also augmented, and detailed time-course studies were performed. Early induction kinetics for ovalbumin and conalbumin synthesis, which differed for each protein, were independent of the dose of oestradiol benzoate injected if it exceeded 0.1 mg/kg. After 6 h for ovalbumin and 2 h for conalbumin, the induction curves diverged according to the dose of hormone administered and in correlation with the persistence of elevated nuclear oestrogen-receptor concentrations, a result confirmed with 11 beta-methoxy-17 alpha-ethynyloestradiol (R 2858), a powerful synthetic oestrogen. When oestradiol benzoate (1 mg/kg) and progesterone (3 mg/kg) were injected simultaneously, the rate of conalbumin sythesis, during the first 6-8 h, was lower than that observed in animals injected with oestradiol benzoate alone. However at later times conalbumin synthesis was greater in animals receiving both hormones than with oestradiol alone. In contrast, the rate of ovalbumin synthesis after the combined injection was higher than that induced by either hormone alone throughout the entire experimental period. In order to study further the synergistic and antagonistic activities of these two hormones, a single injection of progesterone (3 mg/kg) was administered 6, 12 or 18 h after 1.5 mg/kg oestradiol benzoate. Progesterone administration resulted in a reduction in cytoplasmic, nuclear and total oestrogen receptor concentration for at least 6 h when compared with the values in birds treated with oestrogen alone. DNA polymerase and protein kinase activities were also reduced during this period. Subsequently, all parameters increased, and by 18-24 h after progesterone treatment, reached values higher than those observed in animals receiving oestrogen alone.

[Effects of estradiol-7 alpha-butyric acid on hypothalamus cells]

When Rat uterus was incubated at 37 degrees with estradiol-7 alpha-butyric acid (OII-7 alpha-bu), no interference was observed with the intracellular estradiol receptors. In addition, OII-7 alpha-bu did not display estrogenic effect such as in vivo inhibition of LH secretion in Rat and in vitro increased activity of the enzyme ornithine-decarboxylase in the chick oviduct. Contrary to these negative findings, we have observed preoptic and septal cells in the guinea pig where micro-iontophoresis of OII-7 alpha-bu triggers changes of the electric activity within a second. We submit therefore, that this latter response is due to an interaction between the acid estrogen and the neuron membrane.

Soluble biospecific macromolecule for purification of estrogen receptor

An alternative to affinity chromatography purification of proteins based on the use of a water-soluble biospecific polymer has been applied to the estrogen receptor from calf uterus. The receptor (4S-trypsin form) was bound to a dextran-estradiol conjugate (molecular weight approximately 500,000) and the complex was isolated by gel filtration. Highly purified receptor was subsequently released from the dextran-estradiol conjugate by exchange with [3H]estradiol.

Progesterone receptors in the chick oviduct. Determination of the total concentration of binding sites in the cytosol and nuclear fraction and effect of progesterone on their distribution

1. Exchange techniques were developed for measurement of total progesterone receptor binding sites concentration in the cytosol and nuclei of chicken oviduct. 2. The level of progesterone receptor in the cytosol was under both oestrogen and progesterone control. Primary stimulation by oestradiol benzoate increased the receptor concentration from approximately 10 000 sites/cell to approximately 40 000 sites/cell in the magnum cytosol; subsequent withdrawal from oestrogen treatment led to a decrease to approximately 14 000 sites/cell after 6 weeks. After progesterone administration (3 mg/kg) to oestrogen-stimulated, withdrawn chicken, the receptor concentration decreased to approximately 40% of the initial level within the first 4 h; afterwards the receptor level rose again and by 40 h exceeded slightly the initial one. 3. The nuclear levels of the receptor reached a maximum at 1 h after the progesterone injection; however, the gain of the binding sites by the nuclei (approximately 900/nucleus) did not account for their loss from the cytosol. The maximum nuclear receptor level was not influenced by the dose of progesterone within range of 1-10 mg/kg. 4. The extractibility of the nuclear progesterone receptor by 0.5 M NaCl was strongly influenced by preincubation of the nuclei at 30 degrees C; irrespective of this preincubation, approximately 12% of the nuclear receptor resisted extraction with 2 M NaCl/5 M urea.

Oestrogen receptors in chick oviduct. Characterization and subcellular distribution

Macromolecular components with properties of oestrogen receptors have been identified in the 0.5 M KCl nuclear soluble, the nuclear insoluble and the cytosol fractions of laying hen and immature (2--4 weeks, untreated by hormone) chicken oviduct. 7n the 0.5 M KCl extract of laying hen oviduct nuclei, a receptor, of protein nature according to the effects of enzymic treatments, has been identified. It exhibits high affinity for oestradiol with an apparent equilibrium association constant KA = 4 - 109 M-1 at 4 degrees C. The binding of [3H] oestradiol is abolished by 1 muM oestriol, oestrone and diethylstilboestrol, but not by the same concentration of progesterone, testosterone, and cortisol. Sucrose gradient ultracentrifugation studies in the presence of 0.5 M KCl indicate a sedimentation coefficient of 4.3 S, and there is partial aggregation in low-ionic-strength medium. The estimated number of binding sites per nucleus is about 5000, as calculated from DNA content of chick diploid genome. Most of the binding sites were found to be occupied by endogenous oestrogen(s). Oestradiol dissociates from the receptor according to an apparent two-step mechanism. The half-life time for the faster dissociation step is 18 h at 0 degrees C, 25 min at 20 degrees C and 10 min at 30 degrees C, and for the slower one is 180 h, 115 min and 60 min, respectively. In the 0.5 M KCl extract of immature chicken oviduct nuclei, there are approximately 500 receptor sites per nucleus; their affinity for oestradiol is the same as in the case of laying hen soluble nuclear receptor. After repeated extractions of nuclei with 0.5 M KCl medium, a substantial quantity of oestrogen binding sites remains in the residual fraction. Binding characteristics of this insoluble nuclear receptor resemble those of the soluble nuclear receptor: high affinity for oestradiol (KA = 7 - 10(8) M-1 at 37 degrees C) and specificity for oestrogens. The estimated number of binding sites are approximately 2000/cell for laying hen, and approximately 1000/cell for immature chicken. In the high-speed supernatant fraction of laying hen oviduct homogenates, an oestrogen receptor is also present, but its concentration is low (less than or equal to 100 sites/cell) and at the limits of sensitivity of the methods used. In the cytosol of immature chicken oviduct, there are approximately 2500 oestradiol receptor sites per cell.

Dynamics of oestrogen-receptor distribution between the cytosol and nuclear fractions of immature rat uterus after oestradiol administration

1. The nuclear-myofibrilar (800g pellet) fraction of the uterus from immature (22-23 days old) rats not exposed to oestrogen exhibits saturable binding of oestradiol. The nuclear binding capacity represents approximately 10% of that of the cytosol fraction (approx. 3.5 fmol/mug of DNA). The predominant part (0.3.5 fmol/mug of DNA) of the nuclear binind sites are present in the residual pellet after extraction with 0.5 M-KC1. 2. By using an exchange technique in vitro, determinations of the nuclear binding sites have been carried out after administration of 1 mug of oestradiol in vivo. Within 0.5h after the hormone injection, the concentration of nuclear bindng sites increased to approx. 0.4 fmol/mug of DNA in the 0.5 M-KC1-extractable fraction, and to approx. 1.2 fmol/mug of DNA in the residual fraction. Meanwhile the cytosol oestrogen-receptor concentration decreased to approx. 10% of its initial value. In the following period from 0.5 h after the oestradiol injection onwards, the concentration of nuclear oestrogen receptors decreased with halflife values of approx. 140 and 200 min for the KC1(0.5 M)-extractable and residual form respectively. At the same time, the cytosol receptor concentration increased to reach approx. 50% of the initial value by the 6h. This increase could not be blocked by cycloheximide. The initial concentration of cytosol receptor was restored approx. 11h after the injection and the increase during the 6-11h period was sensitive to cycloheximide inhibition, suggesting protein-synthesis-dependence of the process. 3. With the (more) physiological dose of oestradiol (0.1 mug), the decrease the cytosol receptor was only 50% by 4h and this was followed by a period (up to 12h after injection) during which the initial concentration was restored. During this period the increase of the receptor can be blocked by cycloheximide.

The measurement of oestradiol and progesterone in plasma from normal, infertile and clomiphene treated women

The use of clomiphene to assess ovarian function in women has been monitored by the determination of plasma oestradiol and progesterone concentrations. The assay of both hormones was carried out on one plasma sample after separation of oestradiol and progesterone by TLC. The oestradiol was determined by double competitive binding to rabbit uterine supernatant (Robertson et al. 1971) and the progesterone by competitive binding to corticosteroid binding globulin. After clomiphene stimulation the oestradiol levels in the follicular and luteal phases exceeded those found in normal cycles; this was also true of progesterone concentrations during the luteal phase. The methods of assay were also used to follow changes in plasma hormone levels during the early stages of pregnancy in hitherto infertile women. These cases included a twin pregnancy and a pregnancy which terminated in abortion at 7 weeks.

The measurement of high-affinity oestradiol receptors in human uterine endometrium and myometrium

The concentration of unoccupied high-affinity oestradiol receptors in the cytosol of human uterine endometrial curettings and biopsy tissue has been determined. In normal specimens, where the day of the menstrual cycle could be assessed histologically, a variation of tissue receptor concentration throughout the cycle was observed showing a maximum at mid-cycle and minima at the beginning and end of the cycle.

The distribution of oestradiol receptor sites in the endometrium and myometrium along the length of the uterus has also been studied. Highest concentrations in the endometrium were found in the fundus and these levels fell progressively to negligible concentrations in the isthmus and cervix. In general, the concentration of receptor sites in biopsy material was lower than in curettings and this observation has been related on the region of the uterus from which the samples were obtained. The concentration of receptor sites in abnormal uterine specimens lay within the normal range.

A double competitive binding method of measuring oestradiol from menstrual cycle plasma with and without the prior purification of oestradiol

Oestradiol was determined in menstrual cycle plasma by a double competitive binding assay method applied with and without TLC purification of the steroid. The evaporated ether extract from plasma or from the oestradiol zone of a thin layer plate was incubated with a limited excess of rabbit uterine cytosol containing oestradiol receptor. The specificity and affinity of the receptor protein ensured the preferential binding of oestradiol to the virtual exclusion of other oestrogens and weak contaminating competitors introduced by the procedure. These unbound compounds were removed by charcoal incubation. The remaining supernatant was heat-treated to denature the receptor protein and the released oestradiol was determined by competitive binding with rabbit uterine oestradiol receptors. The methods have the advantage of high specificity; the direct assay which excludes the TLC step, is rapid, sensitive and suitable for the routine examination of normal menstrual cycles.