Search

Das hypothalamische Decapeptid Gonadotropin-Releasing-Hormon (GnRH) bindet an spezifische Membranrezeptoren der gonadotropen Hypophysenvorderlappenzelle und bewirkt die Freisetzung von Gonadotropinen. Die Aktivierung der Rezeptoren fuhrt zur Hydrolyse von Membranphospholipiden mit der Freisetzung von Inositoltriphosphat (IP3) und Diacylglycerol (DG). Beide fungieren als „second messenger“. IP3 fuhrt zur Mobilisierung von Kalzium (Ca2 + ) aus intrazellularen Speichern, wahrend DG die Proteinkinase C (PKC) aktiviert. Die Erhohung der intrazellularen Ca2 + -Konzentration ([Ca2 + ]i) ist das wichtigste Signal fur die Initiierung der Gonadotropinsekretion. Die PKC spielt sowohl bei der Exozytose als auch bei der Neusynthese von Gonadotropinen eine Rolle. Die Wirkung von GnRH auf die Gonadotropinsekretion wird in erheblichem Mas durch ovarielle Steroide beeinflust. Inhibitorische und stimulatorische Effekte von Ostradiol und Progesteron konnen durch Modulation von Signaltransduktionsmechanismen vermittelt werden. GnRH-Analoga binden ebenfalls an den GnRH-Rezeptor; GnRH-Agonisten (GnRHag) bewirken wie das naturliche GnRH zunachst eine Freisetzung von Gonadotropinen, spater kommt es durch homologe Desensitisierung zu einer Suppression der Gonadotropinsekretion. Demgegenuber fuhrt die Applikation von GnRH-Antagonisten (GnRHant) sofort zu einer Suppression der Gonadotropinsekretion. Dieser Effekt beruht auf einer kompetitiven Hemmung der Bindung von GnRH an den hypophysaren Rezeptor. Das Fehlen der initialen Steigerung der Gonadotropinsekretion verleiht den GnRHant bezuglich des Therapieziels eine gewisse Uberlegenheit. Diese macht sie fur bestimmte Indikationen zu den Medikamenten der Wahl.

4-Hydroxyestrone 4-methyl ether (4-OHE1 4-Me) was converted to its 17-(O-carboxymethyl)oxime and then coupled to bovine serum albumin. The injection of this steroid-protein conjugate into rabbits induced the formation of antibodies with high specificity and affinity for 4-OHE1 4-Me. With this antiserum a radioimmunoassay was developed which allowed the measurement of 4-OHE1 4-Me with a lower limit of detection of 6 pg/tube. Using a simple and practicable method for the hydrolysis and purification of urine, the excretion rates of 4-OHE1 4-Me were reliably measured in healthy human subjects: male children 0.1 microgram/24 h, female children 0.2 micrograms/24 h, men (20-45 years) 0.7 micrograms/24 h, men (greater than 50 years) 0.5 micrograms/24 h, women, follic. 0.5 micrograms/24 h, periov. 0.6 micrograms/24 h, luteal 0.6 micrograms/24 h, women pregn., first trim. 2.3 micrograms/24 h, sec. trim. 2.9 micrograms/24 h, third trim. 5 micrograms/24 h, women postmenop. 0.5 micrograms/24 h. These urinary excretion rates of 4-OHE1 4-Me are significantly lower than those of 4-hydroxyestrone. Comparing the ratios 4-OHE1 4-Me/4-hydroxyestrone with those of 2-hydroxyestrone 2-methyl ether/2-hydroxyestrone, it becomes obvious that endogenous 4-hydroxyestrogens are methylated in vivo to a much lesser extent than the isomeric 2-hydroxyestrogens, a finding which could partly explain why 4-hydroxyestrogens have higher biologic potencies than their 2-hydroxylated isomers

Cultured pituitary cells from adult female rats were treated for 4 or 24 h in the absence or presence of E2 (10−9 mol/1) with increasing concentrations of the transcription inhibitor actinomycin-D or the translation inhibitor puromycin. During the last 4 h of incubation, LH release was stimulated with 5 × 10−10 mol/1 GnRH. The positive E2 effect observed after 24 h treatment with the steroid was clearly abolished by actinomycin-D at concentrations ≥10−10 mol/1 and by puromycin at concentrations ≥ 10−5 mol/1. These findings indicate that the positive E2 effect on GnRH-induced LH release is fully dependent on intact mRNA and protein synthesis. The negative E2 effect observed after 4 h treatment with the steroid was not affected by actinomycin-D and abolished by puromycin only at concentrations ≥ 10−4 mol/1. Similar results were obtained, when cells had been treated for 4 h with actinomycin-D or puromycin before the 4 h E2 treatment started. Thus, the negative E2 effect seems to be independent of mRNA synthesis and dependent on protein synthesis to a lesser extent than the positive E2 effect. In an attempt to identify positively the subcellular mechanism via which E2 exerts its negative effect, several steps in the GnRH stimulus secretion coupling mechanism were checked whether or not they are modulated by E2. The negative effects of E2 (10−9 mol/1) on LH release induced by GnRH (10−10, 10−9 mol/1) and by the activators of voltage dependent Ca2+ channels K+ (64 mmol/1) or veratridine (3.3 × 10−5 mol/1) were comparable to those of the calcium antagonist verapamil (10−6 mol/1). These findings supported the speculation that E2 might act on the Ca2+ channels. The LH release induced by the Ca2+ ionophores A 23 187 (10 −4 mol/1) or ionomycin (6.6 × 10−5 mol/1), however, was also significantly reduced by 10−9 mol/1 E2, indicating that the steroid modulated a mechanism secondary to the increase of intracellular Ca2+. Also GnRH (10−9, 10−8 mol/1) induced accumulation of [3H]inositol phosphates was not influenced by E2 (10−9 mol/1) treatment, though the steroid exerted a significant negative effect on the LH release by these cells, indicating that phosphatidylinositol-4,5-biphosphate breakdown is not the point of attack for the estrogen. The LH release induced by the activation of protein kinase C with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA, 10−7 mol/1) or with the synthetic diacylglycerol 1,2-dioleyl-sn-glycerol (DOG, 5 × 10−5 mol/1, 10−4 mol/1) was significantly reduced by E2 treatment. These findings give rise to the speculation that E2 might exert its negative effect on GnRH-induced LH release in cultured pituitary cells at the level of protein kinase C or a mechanism secondary to the activation of this enzyme.

Ovariectomized ewes were infused over a period of 12 h at constant rates with different doses of the catecholoestrogen 4-hydroxyoestradiol (4-OHE2) or the primary oestrogen oestradiol (E2) via a catheter placed in the right atrium. Blood samples were drawn every hour for a total period of 48 h starting 1 h before the beginning of the steroid infusion. Luteinizing hormone (LH), 4-OHE2 and E2 concentrations were measured in these samples by specific radioimmunoassays. Infusions of low doses E2 (0.5 μg/h) or 4-OHE2 (2 μg/h) caused only a suppression of LH-secretion. At doses of 1 μg E2/h or 5 μg 4-OHE2/h this negative effect was followed by inconsistent elevations of plasma LH. Beyond this threshold dose, E2 at infusion rates of 2, 5 and 10 μg/h and 4-OHE2 at infusion rates of 10, 25 and 50 μg/h produced the negative effect and massive LH-surges. At still higher infusion rates (E2: 20 μg/h, 4-OHE2: 100 μg/h) lower elevations of plasma LH levels were observed. 4-OHE2 had to be infused at 4–5 times higher rates than E2 to obtain comparable plasma concentrations of either oestrogen. Under this condition the effects of 4-OHE2 and E2 were similar indicating that 4-OHE2 has the same potency as E2 at central target sites.

Dispersed pituitary cells from adult female rats were preincubated for different time periods (0– 12 h) in the absence or presence of 10−9 moestradiol (E2) or 4-hydroxyoestradiol (4-OHE2). Then the media were changed and the cells incubated for 4 h with either vehicle, or E2, or 4-OHE2 and additionally with different concentrations (10−11– 10−7 m) of gonadotrophin-releasing hormone (GnRH). Treatment of pituitary cells with E2 for 4 h (i.e. no preincubation with E2) significantly decreased the LH-response to GnRH at concentrations ≥ 10−10 m of the decapeptide. During a transition time of approximately 10 h (i.e. in cultures preincubated with E2 or vehicle for 2, 4, 6 or 8 h and then coincubated with E2 or vehicle and GnRH for 4 h) no differences between E2-and vehicle-treated cultures were observed. After 14 and 16 h of E2-treatment (i.e. 10 or 12 h preincubation and 4 h coincubation with GnRH) the LH-responses to GnRH in these cultures were significantly higher than in the respective controls. A nearly identical reaction pattern was observed when 4-OHE2 was used instead of E2. In a second series of experiments dispersed rat pituitary cells were suspended in a carrier gel and continuously perifused with medium, using small chromatography columns. When these cells were exposed for 4 min to 10−9 m GnRH at 60 or 48 min intervals, they reacted with reproducible pulsatile LH-discharges during at least 6 subsequent stimuli with the decapeptide. When E2 (10−9 m) was added to the perifusion medium, the LH-responses to GnRH were significantly reduced, starting 36 min after the onset of E2-treatment. These data indicate: 1) In the rat, the negative oestrogen effect is at least in part directly mediated at the pituitary level. 2) The sensitizing effect of oestrogens on rat gonadotrophs to GnRH is significant already after 14 to 16 h. 3) E2 and the catecholoestrogen 4-OHE2 have the same effects in this system. 4) The negative E2-effect on GnRH-induced LH-release is significant after only 36 min, a finding bringing up the question of a non-genomic mechanism.

Under the protection of ascorbic acid a 2-hydroxyestrone bovine serum albumin conjugate was prepared containing intact 2-hydroxyestrone as determined by gas chromatographymass spectrometry. Using this antigen highly specific antibodies were raised in rabbits. Cross-reactivity for 2-hydroxyestradiol and 2-hydroxyestriol was 26 and 4.5%, respectively. An assay procedure of 2-hydroxyestrone in human plasma is described. Using special precautions the assay allows the determination of 2-hydroxyestrone in plasma samples of women (50–95 pg/ml), pregnant women (105–220 pg/ml), men (45–65 pg/ml) and children (20–40 pg/ml).

Short-term (0.5-4 h) treatment of rat pituitary cells in culture with estradiol (E2) results in a significant decrease of Gonadotropin-Releasing Hormone (GnRH) induced LH-release. We studied whether changes in the concentrations of GnRH-receptors (GnRH-R) might account for this phenomenon: pituitary cells from adult female rats were incubated for 4 or 24 h in the presence or absence of 10(-9) M E2. Then saturation curves of D-Ala6-des-Gly10-GnRH ethylamide binding were obtained. In addition, binding studies were carried out in cultures incubated for 0.5, 1, 2 or 4 h with or without 10(-9) M E2 using a near saturating concentration of GnRH-analog. No changes of GnRH-R affinity occurred (4 h experiments: Ka in vehicle treated cells: 0.94 +/- 0.2 x 10(9) M-1, Ka in E2 treated cells: 1.06 +/- 0.3 x 10(9) M-1; 24 h experiments: Ka vehicle: 0.95 +/- 0.2 x 10(9) M-1, Ka E2: 0.82 +/- 0.3 x 10(9) M-1). The GnRH-R concentrations, however, were significantly reduced (44 +/- 3%; P less than 0.001) by 4 h E2 treatment and increased (by 68 +/- 8%; P less than 0.01) by 24 h of E2 treatment. The GnRH induced LH-release in aliquots of the same cell preparations was significantly reduced after 4 h and markedly increased after 24 h of E2 treatment. The experiments on the time-course of the reduction of D-Ala6-GnRH-binding by E2 treatment showed that the number of GnRH-R was significantly decreased (24 +/- 1%; P less than 0.05) already after 0.5 h of exposure to the estrogen. This is also the time period after which the negative E2-effect on GnRH-induced LH-release becomes significant. These data provide first evidence that the short-term negative E2-effect on GnRH induced LH-release by rat pituitary cells in culture could be mediated via a reduction of available GnRH-R.

Portions of pregnancy and midcycle urines were submitted to hot acid hydrolysis, extracted with benzene/ethyl acetate and the extracts washed with ascorbic acid buffer. From the remaining organic phase the catecholestrogens were removed with borate buffer and further purified on Sephadex LH-20 columns. After derivatisation 4-hydroxyestrone was separated from the isomeric 2-hydroxyestrone peak were identical with that of authentic 4-hydroxyestrone. After treatment of the extracts with sodium borohydride 4-hydroxyestradiol-17 beta was identified by GC-MS. By the addition of trace amounts of tritiated 4-hydroxyestrone a recovery of 40% was calculated. On the basis of this recovery and the peak heights of the gas chromatograms an excretion of 4 microgram (midcycle) and 40 microgram (pregnancy) of 4-hydroxyestrone/24 h was estimated.

The effects of RU 486 on the modulation of LH release by progesterone were investigated in cultured anterior pituitary cells from ovariectomized adult female rats. The inhibitory effect of progesterone on LH secretion was demonstrable in estrogen-treated pituitary cells, in which addition of 10(-6) M progesterone to cells cultured in the presence of 10(-9) M estradiol for 52 h reduced the LH response to GnRH (10(-11) to 10(-7) M). When RU 486 was superimposed upon such combined treatment with estradiol and progesterone, the suppressive effect of progesterone on GnRH-induced LH release was completely abolished. The converse (facilitatory) effect of progesterone on LH secretion was observed in pituitary cells pretreated with 10(-9) M estradiol for 48 h and then with 10(-6) M progesterone for 4 h. When RU 486 was added together with progesterone during the 4 h treatment period, the facilitatory effect of progesterone was blocked and LH release fell to below the corresponding control value. The direct effect of RU 486 on LH secretion in the absence of exogenous progesterone was evaluated in cells cultured in the absence or presence of 10(-9) M estradiol and then treated for 4 to 24 h with increasing concentrations of RU 486 (10(-12) to 10(-5) M) and stimulated with GnRH (10(-9) M) during the last 3 h of incubation. In estrogen-deficient cultures, 4 h exposure to RU 486 concentrations of 10(-6) M and above decreased the LH response to GnRH by up to 50%. In cultures pretreated with 10(-9) M estradiol, GnRH-stimulated LH responses was inhibited by much lower RU 486 concentrations, of 10(-9) M and above. After 24 h of incubation the effects of RU 486 were similar in control and estradiol-pretreated pituitary cell cultures. Thus, RU 486 alone has a significant inhibitory effect on LH secretion that is enhanced in the presence of estrogen. The antiprogestin is also a potent antagonist of both the inhibitory and the facilitatory actions of progesterone upon pituitary gonadotropin release in vitro.

As a first step to investigate whether gonadotropin releasing hormone (GnRH) analogs might be able to modulate directly the proliferation of human epithelial ovarian carcinomata, we checked if binding sites for GnRH are present in these malignancies. Specific binding of [ 125 I][d-Ala 6 -des Gly 10 ]-GnRH-ethylamide (GnRH agonist=GnRH-A) could be demonstrated in plasma membranes from 32 out of 40 ovarian carcinomata tested. This binding was dependent on temperature, time and plasma membrane concentration. Mathematical analysis of the binding data showed that the interaction of GnRH-A with the binding sites was consistent with a single class of low affinity, high capacity binding sites (K a = 1.42 ± 0.14 × 10 5 M −1 ; range: 0.3 – 3.8 × 10 5 M −1 ; R=209 ± 69 × 10 −12 M/mg membrane protein; range 16–400 × 10 −12 M/mg MP; x ¯ S.E., n = 32). Native GnRH and the GnRH antagonist [d-p-Glu 1 ,d-Phe 2 ,d-Trp 3,6 ]-GnRH had K a values comparable to those of the GnRH-A used. [ 125 I]GnRH-A binding could not be displaced by oxytocin, thyrotropin releasing hormone and corticotropin releasing factor in concentrations up to 10 −4 M . Somatostatin cross-reacted with binding sites from some carcinomata, while it did not displace GnRH-A binding in membranes from others. Though the functional role of this specific binding site for GnRH in human epithelial ovarian carcinomata is still obscure, it might be part of an autocrine regulatory system and provide a possible point of attack for therapeutic approaches using GnRH analogs in this malignancy.

Equimolar amounts (36.8 nmol) of estradiol and the two catecholestrogens (CE's) 4-hydroxyestradiol (4-OHE2) and 2-hydroxyestradiol (2-OHE2) were injected subcutaneously to ovariectomized adult rats. Serum levels of both LH and FSH were determined at short-term intervals. Moreover, serum levels of the administered steroids and their main free and conjugated metabolites were monitored. Serum levels of the injected steroids reached peak values at different time points: estradiol between 60 and 240 min, CE's between 30 and 60 min. Peak height also differed significantly: with estradiol highest (1500 pg/ml), followed by 4-OHE2 (540 pg/ml) and then 2-OHE2 (135 pg/ml) (ratio 11:4:1). This mirrored the different MCR's of the steroids: CE's, especially 2-OHE2, were rapidly and extensively methylated and/or - to a lesser degree - conjugated. Estradiol remained mainly unchanged. LH-serum levels in steroid treated animals showed - irrespective of the steroid used - a uniform reaction pattern: they were significantly depressed 60 to 240 min after injection and - with the exception of estradiol treated rats - reached pretreatment levels again 480 min after injection. Ultra-short (15 min) effects were not observed. FSH serum levels in CE treated animals were not significantly altered, only E2 application led to a significant but small decrease in FSH levels 240 and 480 min after its injection. In conclusion, neither the effect of 4-OHE2 nor that of 2-OHE2 corresponded to the different MCR's or the MCR-corrected affinities for the classical estrogen receptor. A non-genomic mechanism may be responsible for this impaired effect of CE's.

Primary pituitary cell cultures from adult female rats were incubated for 4 or 24 h with various concentrations of estradiol (E2) or the antiestrogens (AE) tamoxifen (TMX), 4-hydroxytamoxifen (OH-TMX), and clomiphene citrate (CC). The luteinizing hormone (LH)-response of these cultures to gonadotrophin releasing hormone (GnRH) was monitored. Treatment for 4 or 24 h with high concentrations (10(-5) M) of the AE significantly decreased the GnRH-induced LH-release by the gonadotrophs. The negative E2-effect, which is observed in this model after 4 h was enhanced and the positive E2-effect, which occurs after 24 h, was completely reversed into a negative effect by these high AE-concentrations. Treatment of pituitary cells with increasing concentrations of E2 (10(-13)-10(-6) M) or AE (10(-12)-10(-5) M) for 24 h led first to a dose dependent increase of the LH-response to 5 X 10(-10) M GnRH. At higher E2- or AE-concentrations this positive effect was lost, resulting in bell shaped dose-response curves. The following maximal effective concentrations (EDmax) were found: E2 = 10(-10) M, OH-TMX = 10(-9) M, CC = 10(-7) M, TMX = 10(-6) M. Incubation of pituitary cells for 24 h with concentrations of AE near their EDmax and stimulation with increasing concentrations (10(-11)-10(-7) M) of GnRH resulted in significant increases of LH-secretion over a wide range of GnRH-concentrations. It is concluded that AE possess marked intrinsic activities on pituitary LH-secretion: at extremely high concentrations they suppress the GnRH-induced release of the gonadotrophin. At lower concentrations they increase the pituitary LH-response to GnRH in a manner which is qualitatively indistinguishable from that of E2.

The sensitizing effect of oestrogens on GnRH-stimulated LH release was evaluated in pituitary cells from adult female rats, cultured for 2 days in the presence of 10−13 to 10−6 m concentrations of oestradiol and selected A- and D-ring modified oestrogens. With almost all steroids tested, bell-shaped dose-response curves with comparable LH-maxima but different EDmax values were obtained for the LH response to a submaximal GnRH stimulus (5 × 10−10 m). Maximal LH response to 5 × 10−10 m GnRH were found at the following oestrogen concentrations: oestradiol and 4-hydroxyoestradiol = 10−11 m; 2-methyloestradiol = 10−9 m; 2-hydroxyoestradiol = 10−8 m; with 4-methyloestradiol no significant maximum was observed. When cells were pretreated with 10−13, 10−11 and 10−9 m oestradiol, or 4-hydroxyoestradiol, or 2-hydroxyoestradiol, and exposed to increasing concentrations of GnRH (10−11 to 10−7 m), an almost 10-fold decrease in the ED50 for GnRH was observed after pretreatment with 10−11 m oestradiol and 4-hydroxyoestradiol. With 2-hydroxyoestradiol at this concentration, the sensitizing effect was much less pronounced. Increasing the steroid concentration to 10−9 m slightly decreased the effect of oestradiol and 4-hydroxyoestradiol, whereas it increased the effect of 2-hydroxyoestradiol. Thus, at the target cell 4-hydroxyoestradiol has the same potency as oestradiol, while 2-hydroxyoestradiol is significantly less active. The sensitizing effect of oestradiol is only slightly decreased by the presence of a methyl group in position 2, but is markedly reduced by a methyl group in position 4. Our results also demonstrate the high sensitivity of the pituitary to oestrogen-induced enhancement of GnRH-stimulated gonadotrophin release, as well as the decrease of the positive effect at high oestrogen concentrations. The bell-shaped dose-response curves for oestrogen action should be taken into account when evaluating the effects of oestrogens and their derivatives upon gonadotrophin release from the pituitary gland.

Eine der Ursachen weiblicher Infertilitat ist die Besiedelung des Genitale mit pathologischen Erregern. Besondere Bedeutung besitzen hierbei die Chlamydien [2]. Veranderungen im Hormonstatus konnen zu pathologischer Keimbesiedelung fuhren [1]. Ein uberproportionales Wachstum pathologischer Erreger scheint zu Veranderungen des zytologischen Bildes beizutragen [7].

Ovariectomized ewes were infused for different times (2–24 h) during the breeding season (September to Februray) with oestradiol (E2, 2 μg/h) or the catecholoestrogen 4-hydroxyoestradiol (4-OHE2, 10 μg/h). At these infusion rates comparable plasma levels of E2 and 4-OHE2 were obtained when steady state was reached after 3 h (E2: 20 ± 4 pg/ml; 4-OHE2: 22 ± 3 pg/ml). When E2 was infused for at least 6 h, all animals had significant LH-surges, starting 14-16 h after the beginning of oestrogen treatment, even when E2 was infused for up to 24 h. 4-OHE2, however, had only to be infused for 4 h to induce significant LH-surges in all animals tested. When E2 was infused for 12 h at a rate of 100 μg/h, the LH-surges in these ewes were significantly lower than the LH-surges in the same animals treated for 12 h with E2at a rate of 2 μg/h. These data indicate: Once E2 has been administered at a specific infusion rate for a critical time period of 6 h, LH-surges occur, no matter whether the E2-infusion is continued or stopped. For the catecholoestrogen 4-OHE2 this critical time period amounts only to 4 h, if comparable plasma levels of either oestrogen are achieved. This might hint at a prolonged intracellular action of 4-OHE2 as compared to E2. At extremely high infusion rates of E2 (100 μg/h for 12 h) the positive oestrogen effect is significantly impaired, a finding supporting the concept of a bell-shaped dose-response relationship between oestrogens and their positive effect on LH-secretion.

Estrogens substituted in the ortho-position of the phenolic hydroxy-group with an additional hydroxy- or methoxy-group are quantitatively important estrogen metabolites; first isolated and identified from the urine of man and rodents have been demonstrated in blood and different organs, e.g. the pituitary and hypothalamus. The physiological importance of the preeminent representatives of this group, the 2-and 4-hydroxyestrogens, the so-called catecholestrogens, is still equivocal. For example, numerous in vivo investigations in rodents have demonstrated that gonadotrophin secretion is influenced by these catecholestrogens. However, depending on the position of the A-ring substituent, major potency differences have been observed. The significant discrepancies between the quantitative and qualitative effects of catecholestrogens in in vitro and in vivo experiments have been presented and explained on the basis of different receptor affinities and the pharmacokinetics of catecholestrogens. An array of A-ring-substituted steroid model substances has been tested with respect to the effects of 2- and/or 4-substitution on stimulation or blockade of the estrogenic potency.

Die reversible Suppression der gonadotropen Hypophysenfunktion durch Superagonisten des GnRH ermoglicht die Ausschaltung fehlerhafter endogener Gonadotropinsekretion (eugonadotrope Anovulation, Corpus luteum Insuffizienz, PCO-Syndrom) und die Ruhigstellung der Ovarien (PCO-Syndrom, Endometriose) (zur Ubers, vergl. 1). Unter entsprechender Suppression der Hypophysen/ Gonadenachse konnen dann durch exogene Gonadotropine Ovulationen herbeigefuhrt werden.

4-Hydroxyestradiol-17 beta and 4-hydroxyestradiol-17 alpha (5 or 20 microgram/d) were continuously s.c. infused for 3 days into ovariectomized adult rats. The serum levels of either epimer were virtually identical when the same dose was administered. 4-Hydroxyestradiol-17 beta significantly altered body and uterus weight and LH serum levels (negative and positive effects) at both doses tested. 4-Hydroxyestradiol-17 alpha showed no effects even at the 20 microgram/d dose. As both epimers have similar affinities for catechol O-methyltransferase, but their potencies regarding effects on lH serum levels differ markedly, it is concluded that the interaction of catecholestrogens with this enzyme is not essential for their effects on LH release.

Die gonodalen Steroide Ostradiol (E2) und Progesteron (P) konnen die Gonadotropinsekretion direkt auf hypophysarem Niveau beeinflussen. Dies konnte durch Experimente mit Hypophysenzellkulturen nachgewiesen werden [1]. P bewirkt nach Kurzzeitbehandlung eine Steigerung, nach Langzeitbehandlung eine Reduktion der Gonadotropin releasing hormone (GnRH)-stimulierten Sekretion von luteinisierendem Hormon (LH) E2- vorbehandelter Rattenhypophysenzell-kulturen [1, 2]. Wir konnten in einer fruheren Untersuchung zeigen, das RU 486 diese Effekte antagonisiert [2]. Ziel der vorliegenden Studie war es zu untersuchen, ob die neuen Antigestagene ZK 98 299 und ZK 98 734 die P-Wirkungen ebenfalls blockieren und ob evtl. Unterschiede in der Wirkungsweise bestehen.

Application of a commercially available hair lotion containing high concentrations of oestradiol led to uterine bleeding in a 76-year old patient. Histological examination of the endometrium showed typical proliferation. Oestradiol blood levels were in the normal range of the follicular or luteal phase, LH- and FSH-serum concentrations were suppressed. After discontinuing the application of the assay used (20 pg/ml) and gonadotrophins rose to normal postmenopausal levels. These findings prove that after local application of oestradiol on the scalp, percutaneous resorption of the steroid is significant and systemic oestrogen effects have to be taken into account.

Gonadotropin Releasing Hormon (GnRH) wird in der Hypophyse von spezifischen Rezeptoren mit hoher Affinitat und niedriger Kapazitat gebunden. In den letzten Jahren wurden beim Menschen spezifische GnRH-Bindungsstellen auch in anderen Geweben beschrieben: in der Plazenta, im Ovar (Granulosazellen, Corpus luteum) und in Mammakarzinomen. Diese GnRH-Bindungsstellen haben im Gegensatz zu den hypophysaren Rezeptoren eine niedrige Affinitat und eine hohe Kapazitat. Uns gelang der Nachweis solcher spezifischer GnRH-Bindungsstellen in den Zellmembranen von menschlichen epithelialen Ovarialkarzinomen [1]. Diese GnRH-Bindungsstellen sind moglicherweise Teil eines autokrinen Regulationssystems der Tumorzellen. Zu ihrer weiteren Charakterisierung sollte versucht werden, die GnRH-Bindungsstellen in aktiver Form aus der Zellmembran zu solubilisieren.

To provide a definite basis for studies on the biological effects of exogenously administered catecholestrogens, the time courses of the concentrations of these estrogens in serum, pituitary and CNS-tissues were studied in male rats after s.c. injection of either 150 microgram of 4-hydroxyestradiol or 2-hydroxyestradiol (dissolved in 200 microliter sesame oil/ethanol/ascorbic acid; 97.5/2.5/0.1; vol/vol/wt) or equimolar amounts of 4-hydroxyestradiol 3, 4-dibenzoate or 2-hydroxyestradiol 2,3-dibenzoate (dissolved in 200 microliter sesame oil). The injection of free catecholestrogens resulted in bolus-like elevations of the serum and tissue concentrations of the respective compound (max. values up to 9 ng/ml, half-life below 1 h) whereas the injection of catecholestrogen benzoates gave lower (max. values about 1 ng/ml) but prolonged elevations (half-life approx. 24 h and 32 h for 4-OHE2 and 2-OHE2) of the respective free catecholestrogen.