Progestin Receptor Concentrations Research Articles

Simultaneous TLC-densitometric determination of tamoxifen citrate and medroxyprogesterone acetate and UV-degradation kinetic study of medroxyprogesterone acetate.

Coadministration of tamoxifen citrate (TMC) and medroxyprogesterone acetate (MPA) is preferred to increase the response rate and the percentage recovery in patients with endometrial carcinoma. Administration of TMC and MPA and their combination affects estrogen and progestin receptor concentrations in advanced endometrium carcinoma by affecting 17β-hydroxyl steroid dehydrogenase activity and serum hormone concentrations. A sensitive, accurate and robust thin-layer chromatography method has been established for simultaneous analysis of TMC and MPA. Method development was carried out on silica gel F254 using butanol-acetic acid-water (6:0.5:0.5, v/v/v) as mobile phase. Densitometric scanning was carried out at 241 nm for simultaneous detection of TMC and MPA. Retardation factor (Rf ) values for TMC and MPA were 0.21 and 0.85, respectively. The method was validated according to ICH guidelines. Regression plots revealed linear relationships in the concentration range of 50-500 and 25-250 ng/band for TMC and MPA, successively. Accuracy was ≥99.60 and 98.72% for TMC and MPA, respectively. Forced degradation studies using UV photodegradation was applied on MPA after exposure to UV light for different times and applying a kinetic study for calculating the degradation rate constant (k) and half-life time (t1/2 ).

Analysis of androgen-and progestin receptors in human endometrial carcinomas.

Androgen-binding components labeled with a tritiated synthetic androgen, methyltrienolone(R1881) were analysed in human endometrial carcinoma cytosols. Tritiated R1881 binding consists of 3 components; high-affinity, low capacity androgen binding (androgen receptor), possible progestin receptor and non-specific androgen binding. The existence of androgen receptor in the tumor suggests a direct effect of androgen in endometrial carcinoma, possibly, through its interaction with the androgen receptor. Androgen- and progestin receptors were further measured in the cytosols of 20 endometrial carcinomas from 19 non-treated patients. The concentrations of the androgen receptors in the endometrial carcinomas were, in decreasing order; highly differentiated [21.5 + 5.4(SEM) fmoles/mg protein, N=10], moderately differentiated [3.4 + 2.7, N=3] and poorly differentiated tumors [2.5 + 1.4, N=7]. The concentrations of progestin receptors in the highly differentiated, moderately differentiated and poorly differentiated tumors were 291 + 79.7 (N=10), 52.6 + 34.1(3) and 14.7 + 6.8(7), respectively. Androgen- and progestin receptors in endometrial carcinomas would appear to correlate with histologic grade of differentiation of the tumor.

Estrogenic effects of zearalenone on the expression of progestin receptors and sexual behavior in female rats

Zearalenone is a resorcylic acid lactone compound that is produced by fungal infection of edible grains and is believed to influence reproduction by binding to estrogen receptors. In order to study the potential estrogenic effects of this compound in the brain, we examined the effects of zearalenone on the expression of neuronal progestin receptors and feminine sexual behavior in female rats. Ovariectomized rats were treated with zearalenone (0.2, 1.0, or 2.0 mg), estradiol benzoate, or vehicle daily for 3 days. They were then either perfused, and progestin receptors visualized by immunocytochemistry, or injected with progesterone and tested for sexual receptivity with male rats. Progestin receptor-containing cells were counted in the medial preoptic area and ventromedial hypothalamus. The two highest doses of zearalenone increased the concentration of neuronal progestin receptors, as did 10 μg of estradiol. The highest dose of zearalenone (2 mg) also induced progestin receptor staining density comparable to that of 10 μg of estradiol benzoate. In behavioral tests, ovariectomized animals treated with 2 mg of zearalenone followed by progesterone showed levels of sexual receptivity comparable to females treated daily with estradiol benzoate (2 μg) followed by progesterone. These studies suggest that, although structurally distinct and less potent than estradiol, zearalenone can act as an estrogen agonist in the rat brain.

Lordosis-enhancing medial preoptic area lesions do not alter hypothalamic estrogen receptor- or progestin receptor-immunoreactivity in prepubertal female guinea pigs

Female guinea pigs rarely display adult-typical lordosis responses to ovarian steroid hormones until 40–50 days of age. Behavioral hyporesponsiveness in prepubertal females may be due, in part, to deficiencies in hypothalamic estrogen receptors and/or estradiol-induced progestin receptors. This study was designed to test the hypothesis that bilateral medial preoptic area (MPOA) lesions, which enhance the display of progesterone-facilitated lordosis in juvenile females, increase levels of hypothalamic estrogen receptors and/or estradiol-induced progestin receptors. Hartley guinea pigs were ovariectomized at 11–12 days of age and at 14–15 days of age received bilateral electrolytic or sham lesions aimed at the MPOA. At approximately 3 weeks of age, lesioned and sham-lesioned animals were either tested for the display of progesterone-facilitated lordosis or perfused, and their hypothalamic tissue processed for estrogen receptor- or estradiol-induced progestin receptor-immunostaining. Although a significantly higher percentage of MPOA-lesioned than sham-lesioned guinea pigs displayed progesterone-facilitated lordosis (85.7% vs. 5.8%, respectively, p<0.05), there were no significant lesion-related differences in the number or staining intensity of cells containing estrogen receptor- or estradiol-induced progestin receptor-immunoreactivity in the ventrolateral hypothalamus or arcuate nucleus. These data do not support the hypothesis that the enhanced display of progesterone-facilitated lordosis in prepubertal guinea pigs following MPOA lesions is due to increased hypothalamic concentrations of estrogen receptors or estradiol-induced progestin receptors.

Expression of epidermal growth factor receptor (EGFR) in non-affected and tumorous mammary tissue of female dogs

Epidermal growth factor (EGFR), oestrogen (ER), and progestin (PR) receptor concentrations were determined by radioligand binding assay in non-affected mammary tissues (n = 13) and benign (n = 11) and primary/locally recurrent malignant proliferative mammary lesions (n = 45) and metastases (n = 19) in 65 female dogs. The number of specimens expressing EGFR was not significantly different among these tissues, but EGFR concentration was lower in metastases (P = 0.02) than in benign or primary/locally recurrent malignant lesions not mixed with non-affected mammary tissue. The presence of non-affected mammary tissue in primary cancer specimens was noticed as a factor that may influence results of receptor measurements. No relation was found between the expression of EGFR and that of ER or PR in non-affected or in tumorous mammary tissues. It was concluded that in the dog mammary gland EGFR expression is not associated with conditions of steroid receptor absence of biological agressiveness of neoplastic growth.

Immunocytochemical localization of midbrain estrogen receptor‐ and progestin receptor‐containing cells in female guinea pigs

In the guinea pig midbrain, a low concentration of progestin receptors is induced by estradiol. This is in contrast to the mediobasal hypothalamus which has a large number of estradiol-induced progestin receptors. Because the midbrain is an important site for the hormonal regulation of sexual behavior, we mapped the distribution of cells containing estrogen receptor- and estradiol-induced progestin receptor-immunoreactivity in that area. Estrogen receptor-immunoreactive cells are found in midbrain sites previously reported, including the midbrain central gray, the tegmentum lateral and ventral to the central gray, peripeduncular region, and parabrachial nuclei. While progestin receptor-immunoreactive cells were not detected without estradiol priming, estradiol-induced progestin receptors were found throughout the rostrocaudal extent of the midbrain central gray and adjacent tegmental area. Progestin receptor-immunoreactive cells were far fewer than estrogen receptor containing cells, had less cytoplasmic staining, and appeared restricted to the midbrain central gray, lateral and ventrolateral to the cerebral aqueduct and the adjacent tegmental area.

Steroid hormone binding in the harderian gland of birds: characteristics of the androgen, estrogen, and progestin receptors of Anas platyrhynchos and Gallus domesticus

A series of experiments was carried out in immature female chicks and ducks to establish whether the avian Harderian gland contains specific receptors for sex steroids. Cytosol preparations of Harderian glands were submitted to hormone saturation analysis using radiolabeled estradiol, ORG-2058, and dimethylnortestosterone as ligands. In addition, the sedimentation characteristics of the hormone-receptor complexes were studied by ultracentrifugation of linear sucrose gradients. The presence of high affinity binding sites for estrogens ( K d = 2.4 and 1.6 n M), progestins (0.8 and 1.0 n M), and androgens (1.0 and 1.0 n M) was indicated in the chick and duck glands, respectively. The sedimentation coefficients were 7–7.5 S, 7–8 S, and 8 S for estrogen, progestin, and androgen receptor-ligand complexes, respectively. The concentration of the androgen receptor was significantly higher in chick than in duck Harderian glands whereas the estrogen and progestin receptor concentrations were similar in both species. A striking finding was the presence of progestin receptors, which apparently do not exist in the glands of many mammals. Priming with estrogens did not modify the concentration of ORG-2058 binding sites in either species studied, indicating that gland progestin receptor is not estrogen-regulated. Overall the data suggest intracellular mechanisms whereby circulating gonadal hormones regulate avian Harderian gland function.

Development of estradiol‐induced progestin receptor immunoreactivity in the hypothalamus of female guinea pigs

The inability of young female guinea pigs to display progesterone-facilitated lordosis has been attributed, in part, to a deficiency in the concentration of hypothalamic estradiol-induced progestin receptors, as measured by in vitro binding assays. An immunocytochemical technique was used to ascertain where, within the mediobasal hypothalamus, estradiol-induced progestin receptor levels are lower in immature than in adult females. Adult (greater than 7 weeks) and juvenile (3 weeks) ovariectomized females received 10 micrograms estradiol benzoate, a dose that primes adult, but not immature females to respond behaviorally to progesterone. Progestin receptor-immunoreactive (PR-IR) cells were counted in the arcuate nucleus (ARC) and ventrolateral hypothalamus (VLH), the two regions containing the densest populations of estradiol-induced progestin receptors in the mediobasal hypothalamus. There was no age difference in the number of PR-IR cells in the rostral or caudal VLH, but immunostaining was darker in the rostral VLH of juveniles as compared to adults. We found similar numbers of PR-IR cells in the rostral and mid-ARC, but 35% fewer immunostained cells in the caudal ARC of immature, as compared to adult females. Furthermore, staining intensity was weaker in the mid- and caudal ARC of the juvenile females. These data suggest that the ARC, not the VLH, is a site of fewer estradiol-induced progestin receptors in immature females.

Influences of photoperiod on sexual behaviour, neuroendocrine steroid receptors and adenohypophysial hormone secretion and gene expression in female golden hamsters

Exposure to short daylengths arrests the oestrous cycle, provokes daily gonadotrophin surges and reduces the ability of exogenous oestradiol to trigger behavioural receptivity in golden hamsters. In order to examine neuroendocrine effects of photoperiod which might underlie these responses, ovariectomized hamsters were maintained under long or short photoperiods for 54 days before treatment with cholesterol or various doses of oestradiol-17 beta. Short days reduced the ability of low doses of oestrogen to prime hamsters for the induction of oestrus by progesterone. Upon repetition of oestrogen priming 2 weeks later, photoperiod was without significant influence on the concentrations of nuclear oestrogen receptors or cytosolic progestin receptors in a block of tissue containing the hypothalamus and preoptic area. Oestradiol treatment provoked significant increases in serum concentrations of LH and prolactin in the afternoon, but photoperiod did not alter the positive-feedback efficacy of this gonadal steroid hormone. Adenohypophysial LH-beta subunit and prolactin mRNAs were suppressed by short days in ovariectomized hamsters not treated with oestradiol. Oestradiol decreased expression of the LH-beta subunit gene in both stimulatory and inhibitory photoperiods, but increased prolactin mRNA abundance in both long and short days. Photoperiod therefore exerts pronounced steroid-independent effects on phasic LH and prolactin secretion, but regulation of adenohypophysial abundance of LH-beta subunit and prolactin mRNAs by oestradiol is not markedly influenced by daylength. Photoperiodic regulation of the priming effects of oestradiol on behavioural receptivity may result from modulation of events occurring subsequent to steroid-receptor interactions, or involve changes in receptor populations not detectable by the present methods.

Biochemical and Immunocytochemical Assessment of Neural Progestin Receptors Following Estradiol Treatments that Eliminate the Sex Difference in Progesterone‐Facilitated Lordosis in Guinea‐Pigs

Abstract A single injection of estradiol benzoate (10 mug), while highly effective in ovariectomized female guinea-pigs, does not prime castrated males to display progesterone-facilitated lordosis. In contrast, adult males and females exhibit the same, high degree of progesterone-facilitated lordosis when primed with two, 2.0 mug injections of free estradiol-17ss (pulse regimen). We compared neural progestin receptor induction after these different estradiol treatments by in vitro radioligand binding assays and immunocyto-chemistry. Binding assays confirmed previous observations of lower concentrations of cytosol progestin receptors in the mediobasal hypothalamus-preoptic area in estradiol benzoate-treated males than in females. No such sex difference was observed in animals that had been exposed to the behaviorally effective estradiol pulse regimen; rather, hypothalamic-preoptic area progestin receptor concentrations in these animals did not differ from the low levels observed in males treated with the behaviorally ineffective estradiol benzoate regimen. Immunocytochemical analysis revealed progestin receptor-immunoreactivity in fewer cells in the medial preoptic nucleus-anterior hypothalamic nucleus, periventricular preoptic area and arcuate nucleus of estradiol pulse- as compared to estradiol benzoate-treated males and females. Estradiol benzoate treatment induced progestin receptor-immunoreactivity in more cells in the medial preoptic area and ventrolateral hypothalamus than estradiol pulses in males, but not in females. Surprisingly, in these regions estradiol benzoate-treated males had significantly more progestin receptor-immunoreactive cells than females. These experiments yield two major findings: First, as has been shown in rats, the display of progesterone-facilitated lordosis is not inflexibly differentiated according to sex in guinea-pigs. Furthermore, reduced concentrations of estradiol-induced progestin receptors in the hypothalamus and preoptic area cannot account for the lack of progesterone-facilitated lordosis that is observed following priming with estradiol benzoate in males. Secondly, in the medial preoptic area and ventrolateral hypothalamus of female guinea-pigs, estradiol pulses are as effective as estradiol benzoate in inducing progestin receptors. These observations, taken together with the finding of equal behavioral efficacy of the two estradiol treatments, are consistent with the hypothesis that estradiol-induced progestin receptors in these regions of the brain are involved in progesterone-facilitated lordosis in female guinea-pigs.

Influence of O.C.T. embedding compound on determinations of estrogen and progestin receptors in breast cancer.

Estrogen receptor (ER) and progestin receptor (PR) concentrations in tumor biopsies are important predictive indicators of a clinical response to endocrine therapy of breast cancer. To assess interference of O.C.T. (optimum cutting temperature) embedding compound in assays of ER and PR by radioligand binding, we determined specific binding capacities and affinities of ER and PR in cytosols by a multipoint titration method, using split samples of 14 breast-tumor biopsies, one portion serving as untreated control, the other treated with O.C.T. There was no statistically significant difference between these two groups. We then compared these data with those of historical controls analyzed both in the presence and absence of sodium molybdate (10 mmol/L). Eighty breast-tumor specimens (mean +/- SD patients' ages, 59 +/- 14 y) embedded in O.C.T. compound and analyzed without molybdate gave ER and PR values that differed insignificantly from those for 306 samples (patients' ages, 61 +/- 14 y) untreated with O.C.T. Thirty-nine specimens (patients' ages, 58 +/- 15 y) embedded in O.C.T. compound were analyzed in the presence of molybdate and compared with the results for 288 specimens (patients' ages, 61 +/- 14 y) untreated with O.C.T. Again, there was an insignificant difference in the concentrations and affinities of receptors in the two groups. Evidently O.C.T. compound does not alter the receptor status of tumor biopsies.

Non-classical antiestrogenic actions of dexamethasone in variant MCF-7 human breast cancer cells in culture

The aim of this work was to determine whether dexamethasone (Dex), a synthetic glucocorticoid, counteracts the stimulatory effects of estradiol (E 2) on MCF-7 cells. We have shown that Dex inhibits in a dose-dependent fashion the estradiol-stimulated cell proliferation. This inhibition (ID 50 − 5–10 nM), which is complete at 100 nM Dex, is prevented by the antiglucocorticoid RU 486 and is clearly different from that found with trans-4-OH-tamoxifen because the inhibition due to a fixed concentration of Dex is not abolished by a high concentration of estradiol. This inhibitory effect displays some degree of specificity. Progesterone and the progestins R 5020 and ORG 2058 are without effect and Dex does not alter the triiodo- l-thyronine-stimulated cell growth. To characterize further the antiestrogenic action of Dex, the effects of this drug on specific responses to estradiol were studied. (1) Among the positive responses to estradiol two are prevented by Dex (the increase of concentration of progestin receptors and that of immunoreactive insulin-like growth factor I, IR-IGF-I, in conditioned medium) and two are insensitive to Dex (the enhancement of the secretion of 52000 and 160000 M r proteins). (2) A negative response to estradiol (the down-regulation of estrogen receptor) is not prevented but rather accentuated by Dex. Thus, Dex counteracts the stimulatory effects of estradiol on the proliferation of MCF-7 cell variants characterized by progestin insensitivity. This non-classical antiestrogenic effect could be due in part to the attenuation of the E 2-induced IR-IGF-I secretion and, less probably, to the accentuation of the down-regulation of E 2 receptors. It could account for certain therapeutic and/or side effects of glucocorticoids on estrogen target cells.

Long-term ovariectomy and hormone-induced sexual behavior, progestin receptors, and hypothalamic morphology in female rats

Long-term ovariectomy reduces the ability of estradiol and progesterone treatment to induce sexual receptivity in female rats. Previous researchers suggested that this effect may be due to a decreased induction of neural progestin receptors by estradiol in the long-term ovariectomized rats. The present study was designed to replicate and extend this finding, and to search for neuroanatomical correlates by measuring the volume of the ventromedial nucleus (VMN) of the hypothalamus, a putative site of action of estradiol and progesterone for the induction of female sexual behavior. Long-term ovariectomy (5 to 6 weeks) as compared to short-term ovariectomy (1 week) reduced the ability of estradiol-17β and progesterone treatment to induce sexually receptive and proceptive behaviors. Consistent with previous reports, our data show that the reduced levels of cytosol progestin receptors after long-term ovariectomy and estradiol treatment are related to a reduced ability of estradiol to induce the receptors. Long-term ovariectomy did not affect the concentration of cytosol progestin receptors in the preoptic area, suggesting a neuroanatomical specificity to this effect. Contrary to our predictions, long-term ovariectomy did not affect the volume of the VMN. In fact, estradiol treatment, while blocking the effect of long-term ovariectomy on sexual behavior, decreased the volume of the VMN. Therefore, the measurement of the volume of the VMN is not a good predictor of the responsiveness to steroid hormone induction of sexual behavior.

Sexual receptivity in hamsters: Brain nuclear estrogen and cytosolic progestin receptors after single and multiple steroid treatments and during the estrous cycle

This series of experiments investigated the relationship between various treatments consisting of estradiol benzoate (EB) and progesterone (P) on sexual receptivity and on concentrations of nuclear estrogen receptors (NER) and cytosolic progestin receptors (CPR) in the hypothalamus-preoptic area in female hamsters. The injection of 1 μg EB at 0 and 24 hr resulted in higher levels of receptivity (after 0.25 or 0.5 mg P), NER and CPR compared to those obtained after a single injection of 2 μg EB. Animals treated with 5 μg EB at 0 and 24 hr displayed greater levels of receptivity (after 0.5 mg P) and had higher NER concentrations than animals given a single injection of 10 μg EB. Groups treated with either 1 μg EB at 0 hr or 0.5 μg EB at 0 and 24 hr did not differ and showed low levels of receptivity, NER and CPR. NER and CPR were also measured on each day of the estrous cycle. NER levels rose between Days 1 and 2, again between Days 2 and 3, and remained elevated on Day 4. CPR levels increased between Days 2 and 3, and there was no difference between Days 3 and 4. Taken together, these data suggest that receptivity in hamsters after estrogen exposure is correlated with the accumulation and maintenance of relatively high NER levels and on the induction of CPR. This can be accomplished by a single large injection of EB or by smaller split doses.

Development of progesterone-facilitated lordosis in female guinea pigs: relationship to neural estrogen and progestin receptors

Ovariectomized (OVX), 20-day-old female guinea pigs did not exhibit lordosis following treatment with estradiol benzoate (EB) and progesterone. Behavioral responsiveness to EB and progesterone developed abruptly; by 30 days of age, responses typical of adult females (>9weeks of age) were observed. In vitro assays of neural steroid receptors were performed to test the hypothesis that a deficiency in the concentration of hypothalamic and/or preoptic area estrogen and/or progestin receptors contributes to the lack of progesterone-facilitated lordosis in juvenile (20-day-old) females. Assay of cytosol progestin receptors in the mediobasal hypothalamus (MBH) and preoptic area (POA) of immature and adult females 40 h after injection of EB confirmed a previous report that the concentration of estradiol-induced cytosol progestin receptors in the MBH of juvenile females was slightly lower than that observed in adults. Furthermore, MBH cell nuclear accumulation of progestin receptors after progesterone injection was markedly lower (i.e. 42%) in immature, as compared to adult females. The concentrations of cytosol estrogen receptors in the MBH and POA did not differ between immature and adult OVX guinea pigs. Also, cell nuclear estrogen receptor accumulation in the MBH after estradiol injection was comparable in immature and adult females. These data suggest that a deficiency in cell nuclear progestin receptor accumulation in the MBH may contribute to the absence of progesterone-facilitated lordosis in estradiol-primed, immature female guinea pigs. This age-related difference in cell nuclear progestin receptor accumulation may be due, in part, to reduced concentrations of estradiol-induced cytosol progestin receptors. However, the deficient response to estradiol in immature females does not appear to be the result of reduced levels of cytosol estrogen receptors or to aberrant cell nuclear estrogen receptor accumulation in the MBH.

Circulating reproductive hormones and hypothalamic oestradiol and progestin receptors in infertile Zucker rats.

Plasma concentrations of LH, FSH, prolactin and progesterone were measured during the oestrous cycle in obese (fa/fa) and non obese (Fa/?) Zucker rats. In obese rats the mid-afternoon surge of LH during prooestrus was reduced compared with that in non-obese rats (P less than 0.05), and the maximum concentrations of FSH and prolactin declined more slowly during oestrus. Progesterone concentrations were higher during most of the oestrous cycle in obese rats. Oestradiol and progestin receptors were measured in the hypothalamus of female Zucker rats. Lower concentrations of oestradiol receptors were found in the preoptic area of obese rats (P less than 0.05). Concentrations of oestradiol receptors in the medial basal hypothalamus were also lower in obese rats, though the difference was not statistically significant. Concentrations of progestin receptors were similar in both phenotypes in the preoptic area and media basal hypothalamus. It seems likely that the abnormalities in reproductive hormones and oestradiol receptors contribute to the infertility of obese female Zucker rats. The underlying mechanism has still to be determined.

Cytosol estrogen and progesterone receptors in bovine endometrium after uterine involution postpartum and in the estrous cycle

Cytosol estrogen and progestin receptor (ERC and PRC) concentrations in bovine endometrium were investigated. Samples were taken by biopsy after parturition, when uterine involution was completed but before estrous cycles resumed (postpartum anestrus) and thereafter during the follicular phase and at diestrus. The concentration of cytosol estrogen receptor (ERC) was lower in diestrus (375 fmol/mg protein) than during follicular phase (557 fmol/mg protein, P < 0.01) and postpartum anestrus (544 fmol/mg protein, P < 0.05). During the follicular phase, ERC increased from values measured at proestrus (388 fmol/mg protein) to higher concentrations at estrus (550 fmol/mg protein) and metestrus (700 fmol/mg protein). At the beginning of diestrus, ERC levels were observed to decline ( P < 0.05). Progesterone receptor concentrations during postpartum anestrus (1333 fmol/mg cytosol protein) and during the follicular phase (1405 fmol/mg protein) were significantly higher than in diestrus (794 fmol/mg protein). During the follicular phase, PRC concentrations increased from the level measured at proestrus (865 fmol/mg protein) to higher levels at estrus (1366 fmol/mg protein) and metestrus (1909 fmol/mg protein). The rises between proestrus and metestrus ( P < 0.001), as well as between estrus and metestrus ( P < 0.05), were statistically significant. After formation of the corpus luteum, PRC concentrations diminished in the endometrium. Decreasing concentrations of PRC were observed during diestrus until the onset of proestrus. Changes in the concentrations of PRC and ERC were usually parallel. As in several other species, these results are compatible with the thesis that estrogen induces ERC and PRC, whereas progesterone has an opposite effect. No significant differences in PRC or ERC levels were observed between Ayrshire and Friesian breeds, or different feeding groups.

Steroids induce hypothalamic progestin receptors and facilitate female sexual behavior in neonatal rats

This report provides the first evidence that two activational actions of estrogen can occur within the first week of life in the rat. Priming 4-day-old rats with exogenous estradiol benzoate facilitates lordosis and ear wiggling-like behavior, and induces cytosol progestin receptors in the medial basal hypothalamus and preoptic region (Hyp-PoA) 44 h later. Moreover, unprimed male infants show more intense lordosis and higher concentrations of cytosol progestin receptors in Hyp-PoA than infant females. Neonatal castration of male infants decreases their concentration of cytosol progestin receptors in Hyp-PoA to the levels normally seen in infant females. In addition, priming 6-day-old infants with progesterone alone facilitates lordosis in male but not female infants. Together, these data demonstrate that in the male infant, endogenous steroids of testicular origin have activational as well as organizational actions.

Aromatase activity in human ovarian cancer

Eighty-four tumor samples from 70 women with primary ovarian cancer were assayed for cytosol estrogen (ERc) and progestin (PRc) receptor concentrations and aromatase activity. In addition, 22 of the tumors were studied for their response to the aromatase inhibitor, 4-OH-androstenedione, in a soft agar clonogenic cell assay system. Although aromatase activity was detected in almost all of the primary tumors, this enzyme was barely detectable in the majority of metastatic tumor samples. There was no significant correlation between aromatase activity and either the ERc or PRc content of the tumors, or tumor grade. Of 12 tumors grown successfully in the soft agar culture system, only 1 showed a substantial (>50%) reduction in colony-forming efficiency after exposure to the aromatase inhibitor. These results suggest that local estrogen biosynthesis probably does not play an important role in the majority of epithelial ovarian tumors. However, there may be a small subset of estrogen receptor-positive tumors in which aromatase could provide a local growth stimulus.

Assay of oestrogen and progestin receptors in human meningioma cytosols using immunological methods

Oestrogen (ER) and progestin receptors (PR) were assayed in human meningioma cytosol by radioligand binding assay with Scatchard plot analysis and by monoclonal antibody based enzyme immunoassays. For comparison, human breast cancer tissues were used. Results of both assays agreed very well. For human breast cancer, receptor levels assayed with both methods showed a highly significant correlation (ER: r = 0.96; n = 74 and PR: r = 0.95; n = 19). Also for meningioma cytosols a good agreement was observed between the result of both assays. Thus, most meningiomas were devoid of ER but contained significant concentrations of PR. PR levels in meningioma determined with the enzyme immunoassay correlated well with those found by Scatchard plot analysis. After logarithmic transformation of the data the regression line was; PR(EIA) = 0.83 × PR(Scatchard) + 0.36 ( r = 0.917; n = 24). The recognition of the progestin binder in meningioma by a monoclonal antibody against the progestin receptor is a further indication that progestin binding in meningioma occurs to a true receptor.