Comparative study of nuclear binding sites for oestradiol in rat testicular and uterine tissue. Determination of low amounts of specific binding site by an [3H] oestradiol-exchange method

EXPRESSION OF ESTROGEN RECEPTOR α AND PROGESTERONE RECEPTOR IN CHILDREN WITH UNDESCENDED TESTICLE PREVIOUSLY TREATED WITH HUMAN CHORIONIC GONADOTROPIN

PURPOSE

The aim of this study was to investigate expression of estrogen receptor alpha (ERalpha) and progesterone receptor (PR) in paratesticular tissues obtained from boys with undescended testes.

MATERIALS AND METHODS

A total of 65 boys with unilateral cryptorchidism and failed human chorionic gonadotropion treatment underwent orchiopexy. A small sample of gubernaculum, cremasteric muscle and processus vaginalis was obtained. A total of 57 boys who underwent inguinal hernia repair served as the control group. All boys in the control group had testes in the scrotum. The expression of estrogen receptor alpha and progesterone receptor was measured by counting the number of ERalpha or PR positive cells detected by immunohistochemical analysis.

RESULTS

ERalpha and PR density was higher in cremasteric muscle and processus vaginalis obtained from boys with undescended testes than in the control group. Density of progesterone receptor in the examined groups was lower than the density of estrogen receptor.

CONCLUSIONS

ERalpha and PR are expressed in paratesticular tissues important for normal testicular descent. ERalpha was over expressed in cremasteric muscle and processus vaginalis in boys with undescended testes previously treated with human chorionic gonadotropin.

Ontogeny of estrogen receptor-beta expression in rat testis

The recently discovered estrogen receptor-beta (ERbeta) is expressed in rodent and human testes. To obtain insight in the physiological role of ERbeta we have investigated the cell type-specific expression pattern of ERbeta messenger RNA (mRNA) and protein in the testis of rats of various ages by in situ hybridization and immunohistochemistry. In fetal testes of rats 16 days postcoitum and testes of 4-day-old animals, fetal germ cells (gonocytes) reveal the ERbeta mRNA in their cytoplasm and the ERbeta protein in their nucleus. In testes of 11- and 15-day-old rats, ERbeta mRNA and protein were detected in Sertoli cells and type A spermatogonia. No signal was found in other types of germ cells. In the adult testes, expression of ERbeta mRNA as well as ERbeta protein was found in pachytene spermatocytes from epithelial stages VII-XIV and in round spermatids from stages I-VIII. Low ERbeta expression was observed in all type A spermatogonia, including undifferentiated A spermatogonia, whereas no expression was found in In and type B spermatogonia and early spermatocytes. At all ages, Sertoli cells showed a weak hybridization signal as well as weak immunoreactivity for ERbeta. In adult testes, no ERbeta mRNA or protein was detected in the interstitial tissue, indicating that Leydig cells and peritubular myoid cells do not express ERbeta. The expression of ERbeta in fetal and late male germ cells as well as in Sertoli cells suggests that estrogens directly affect germ cells during testicular development and spermatogenesis.

The estrogen receptor beta subtype: a novel mediator of estrogen action in neuroendocrine systems

The recent discovery that an additional estrogen receptor (ERbeta) subtype is present in many rat, mouse, and human tissues has advanced our understanding of the mechanisms underlying estrogen signalling. Ligand-binding experiments have shown specific binding of 17beta-estradiol by ERbeta with an affinity similar to that of ERalpha. The rat tissue distribution and/or the relative level of ERalpha and ERbeta expression seems to be quite different, i.e., moderate to high expression in uterus, testis, pituitary, ovary, kidney, epididymis, and adrenal for ERalpha and prostate, ovary, lung, bladder, brain, bone, uterus, and testis for ERbeta. Within the same organ it often appears that the ER subtypes are expressed in different cell types, supporting the hypothesis that the ER's may have different biological functions. The cell type-specific expression of ERalpha and ERbeta in rat prostate, testis, uterus, ovary, and brain and the distribution of ERbeta mRNA in the ERalpha knock-out mouse brain are discussed. The discovery of ERbeta suggests the existence of two previously unrecognized pathways of estrogen signalling; via the ERbeta subtype in tissues exclusively expressing this subtype and via the formation of heterodimers in tissues expressing both ER subtypes. The existence of two ER subtypes, their differential expression pattern, and different actions on certain response elements could provide explanations for the striking species-, cell-, and promoter-specific actions of estrogens and antiestrogens. The challenge for the future is to unravel the detailed physiological role of each subtype and to use this knowledge to develop the next generation of ER-targeted drugs with improved therapeutic profiles in the treatment or prevention of osteoporosis, cardiovascular system disorders, Alzheimer's disease, breast cancer, and disorders of the urogenital tract.

The actions of calcitonin on the TM3 Leydig cell line and on rat Leydig cell-enriched cultures

Studies demonstrating calcitonin receptors on Leydig cells have suggested that these cells may be one of the many sites affected by this peptide. To investigate this possibility, the effect of synthetic salmon calcitonin on the TM3 Leydig cell line (derived from immature mouse Leydig cells) and on primary Leydig cell-enriched preparations was examined. Synthetic salmon calcitonin stimulated the conversion of [3H]adenine to [3H]cyclic AMP in TM3 cells. In addition, the hormone stimulated the basal secretion of testosterone in both TM3 cell- and Leydig cell-enriched cultures and potentiated the action of hCG on Leydig cell-enriched cultures. Synthetic salmon calcitonin also increased the concentration of androgen and estrogen receptors in cultured TM3 Leydig cells by 2- and 4-fold, respectively, when added to the culture medium (1 micrograms/ml). The fact that 8-bromo-cyclic AMP decreased both androgen and estrogen receptor concentrations suggested that the effect of calcitonin on sex steroid receptors is not mediated by its effect on cyclic AMP in these cells. The possibility that the action of calcitonin on steroid receptors might be mediated by another messenger such as calcium (Ca2+) was therefore considered. Progressively lowering the concentration of Ca2+ in the culture medium of the cells from 1.5 mM to less than 0.01 mM decreased the concentration of both androgen and estrogen receptors. Returning the Ca2+ concentration to normal levels (1.5 mM) restored steroid receptor levels. Receptor levels were also decreased when the extracellular Ca2+ concentration was lowered to 0.5 mM, and treatment with the Ca2+ ionophore, A23187 (1 microM), restored receptor levels to normal. The calcium channel blocker, verapamil, decreased the androgen receptor concentration but unexpectedly increased the concentration of estrogen receptors. It was concluded that calcitonin stimulates cAMP formation and testosterone secretion, and increases the concentration of sex steroid receptors. These observations provide evidence that the previously demonstrated calcitonin receptors on Leydig cells may be coupled to several biologic responses in this cell type.

Depletion-replenishment of the testicular estrogen receptor: sensitivity to cycloheximide and actinomycin D

Male rats (30-35 days old) were utilized to examine the process of depletion and replenishment of the testicular cytosolic estrogen receptor and to investigate the effects of cycloheximide and actinomycin D on these processes. The dose dependence and temporal nature of receptor depletion and replenishment were investigated. Maximum depletion (greater than 90%) occurred by 1 h after in vivo administration of either 5 or 10 micrograms estradiol-17 beta. Depletion of the cytosolic receptor at 1 h occurred concomitant to a marked increase in nuclear receptor thus indicating translocation. Receptor replenishment to control levels was observed by 6 h post treatment. To determine the requirements for transcriptional and translational events in the replenishment process, actinomycin D and cycloheximide were administered in vivo. Simultaneous treatment with cycloheximide and estradiol resulted in a significant inhibition of replenishment at 6 and 12 h post treatment of 46 and 60% below control levels, respectively. Cycloheximide treatment alone had no effect on receptor levels. A significant inhibition of replenishment at 6 h was also shown when cycloheximide was given 3 h after estradiol treatment. Cycloheximide administration at 6 h after estradiol significantly suppressed receptor levels at 12 h suggesting that replenished receptor levels at 6-12 h are in a state of rapid turnover. Receptor replenishment exhibited a different response to actinomycin D treatment in that significant inhibition was observed only when the drug was administered at 3 h after estradiol treatment. These results demonstrate that testicular cytosolic receptor depletion is dose and time dependent. The results further demonstrate that receptor replenishment involves protein synthesis and suggests that synthesis of new RNA might also be required.

The acute effect of oestrogens on testosterone production appears not to be mediated by testicular oestrogen receptors

Scatchard binding analysis was performed to measure the cytoplasmic oestrogen receptor in the testis of rats. After treatment of rats with the antioestrogen tamoxifen no oestrogen receptor binding was found in testicular low speed supernatant between 12 and 96 h after treatment. Such tamoxifen-treated rats were used to study the acute effect of oestrogens on testosterone secretion, both in vivo and in vitro. Injection of oestradiol benzoate (50 microgram, 24 h prior to experiment) resulted in a significant depression of basal and LH-stimulated plasma testosterone levels in control rats and this effect was unchanged in tamoxifen-pretreated rats. In vitro, oestradiol-17 beta also inhibited the LH-induced rise in testosterone secretion by isolated testicular interstitial cells. This inhibition was not affected if the rats had been pretreated with tamoxifen. These results indicate that the inhibitory effects of exogenous oestrogens on testicular testosterone production are probably not mediated by the oestrogen receptor.

Nuclear testosterone receptors in the ovine testis

Nuclear [3H] testosterone-receptor complexes were demonstrated in hypophysectomized ram testis after in vitro direct labelling. The nuclear binding was maximal after a 45 min incubation of the tissue. The receptors are extractable by 0.4 M KC1 or NaSCN with a 25-30% efficiency. They migrate towards the anodic region during electrophoresis on agar gel. Nuclear androgen receptors were characterized in intact lamb testis by a testosterone exchange assay. After precipitation by protamine sulphate, the receptors were labelled with [3H]testosterone during a 12 h incubation at 4 degrees C. The exchange activity was linear between 0.1 and 0.9 mg of DNA per ml of incubation buffer. The receptors bind testosterone with a limited capacity (40-180 fmoles per mg DNA) and a dissociation constant Kd of 2 x 10(-9) M. Their relative affinities for steroids are dihydrotestosterone greater than testosterone greater than estradiol greater than progesterone greater than 5 alpha-androstanediol greater than cyproterone acute greater than R5020.

Estrogen receptors in the male

Estrogens in the male are secreted by the testes and derived extragonadally from the aromatization of certain androgens. In some brain regions critical for the control of gonadotropin secretion and behavior, androgens may be aromatized to estrogens within the cells that are regulated. Estrogen may have other physiological roles on the testes to control testosterone secretion and on accessory sex glands to promote both fibromuscular growth and secretion. High doses of estrogen given for treatment of prostatic cancer or modulation of reproductive function not only reduce testosterone secretion but also interact with the liver, changing the secretion of various plasma proteins and causing several undesirable side effects. The hypothalamus, pituitary, testes, accessory sex glands, and liver all contain an apparently identical protein, the estrogen receptor, which may mediate the actions of estrogen.

The aging Leydig cell: VII. Cytoplasmic estradiol receptors

Plasma estradiol and cytosolic estradiol receptor levels of testes were determined in a group of young (2-3 months) and old (24 months) Sprague-Dawley rats. Estradiol binding sites for the young rats averaged 5.6 +/- 0.3 fmol/mg protein (x +/- SE, n=12), which was comparable to that of the old rats, 5.7 +/- 0.3 fmol/mg protein (n=12). Using Scatchard analyses, the association constants at equilibrium of estradiol receptor binding of the old and young rats were the same, 6.1 x 10 10 M-1. Plasma estradiol levels were also similar in both groups-19.6 +/- 2.8 pg/ml (n=14) for the young and 19.2 +/- 2.6 pg/ml (n=10) for the old rats. Our results suggest that impaired testosterone biosynthesis in old rats was not due to elevated plasma estradiol levels or to differences in testicular estradiol receptor content.

A Leydig cell tumour: a model for the study of lutropin action

The properties of cells isolated from a Leydig cell tumour have been compared with normal rat testis Leydig cells. These cells were found to be similar in the following respects: 1. Lutropin-stimulated cyclic AMP and testosterone production. 2. Lutropin-activated protein kinase activity followed by phosphorylation of endogenous proteins of mol. wts. 57,000and 14,000. 3. Parallel lutropin dose vs. response curves for phosphorylation of the endogenous proteins and for testosterone production. 4. Two forms of isoenzyme, cyclic AMP dependent protein kinase, present. They differed mainly with respect to the lutropin-stimulated testosterone production, which was much lower in the tumour cells compared with the normal adult testis Leydig cells (4.6 +/- 1.1 and 114 +/- 16 ng testosterone/10(6) cells per 2 h, respectively). However, the lutropin-stimulated steroid production in the tumour cells was quantitatively comparable with the normal rat Leydig cell when the metabolism of pregnenolone in intact cells and mitochondria was inhibited by addition of SU-10603 and/or cyanoketone. It is concluded that the Leydig cell tumour used in this study can be used to investigate certain aspects of lutropin action where large quantities of cells are required.

Interactions of chlorinated hydrocarbon pesticides with the 8S estrogen-binding protein in rat testes

The effect of certain DDT analogs on the binding of 3H-estradiol to the 8--9S estrogen binding protein of rat testicular cytosol was studied by sucrose sedimentation analysis. The binding of 3H-estradiol to testicular cytosol was inhibited by o,p'DDT, a DDT analog which is estrogenic in the intact female, but not by p,p'DDE which is a nonestrogen in the female. The pesticide methoxychlor, which is estrogenic in vivo in the female, failed to inhibit 3H-estradiol binding, presumably requiring metabolic activation for binding to the testicular cytosol. In fact, its di-demethylated metabolite 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (HPTE), also estrogenic in vivo, caused marked suppression of 3H-estradiol binding.

Studies on sex-organ development. Changes in chemical composition and oestradiol-binding capacity in chromatin during the differentiation of chick Müllerian ducts

Biochemical and immunochemical techniques were used to probe the changes in composition of the chromatin of differentiating Müllerian ducts. The non-histone protein increases gradually in the left duct and reaches a constant amount at day 15 of incubation, then remains at the same value until after birth. In the regressing right duct, the non-histone protein increases and then decreases. Gel electrophoresis indicated an increased heterogeneity in the composition of the non-histone protein corresponding to Müllerian-duct differentiation. Little variation in quantity and quality of the histone was observed; however, immunochemical assay confirmed the structural change of Müllerian-duct chromatin during development. An antibody against the chromatin of the newborn-chick oviduct was produced in the rabbit. The chromatin of Müllerian ducts from the early embryonic stage showed a small affinity with the antibody; the affinity increased during the late embryonic stages. The affinity was greatly decreased in the regressing right duct. Oestrogen-binding sites were present in the chromatin of the left and right Müllerian ducts during differentiation, with more sites in the left duct than in the right one during the late stages of development. After oestrogen treatment in vivo, the oestrogen-binding sites on the chromatin of both the left and the right ducts were increased, with a greater increase in the left duct than in the right. In the developing left duct the binding sites reach a maximum on day 15 of incubation, and remain constant at that value until birth.

Oestradiol-receptor complexes in subnuclear fractions of rat uterine tissue

The subnuclear distribution of 3H-oestradiol-receptor complexes was studied in uterine tissue of ovariectomized adult rats. Nuclei were sonically disrupted and 8 different subnuclear fractions were isolated by discontinuous sucrose density gradient centrifugation. 3H-Oestradiol-receptor complexes, measured by hydroxylapatite column chromatography, were localized in a light chromatin fraction as well as in a heavy chromatin fraction. Using the hydroxylapatite chromatography technique it was possible to demonstrate three classes of oestradiol-receptor complexes which differ in affinity for the chromatin. Oestradiol-receptor complexes with a high affinity for the chromatin were predominantly localized in the heavy chromatin fraction, whereas complexes with a lower affinity for their acceptor sites were present in the lighter chromatin fraction.