Autoradiographic localization of [3H]hydroxytamoxifen to uterine oestrogen- and antioestrogen-binding sites

Summary Immature rats were injected subcutaneously with 0.36 g of [³H]hydroxytamoxifen ([³H]TAM(OH)) or 0.24 g of [³H]oestradiol in oil, and 4 h later uteri were processed for thaw-mount autoradiography. The specificity of [³H]TAM(OH) localization was determined by injecting a 200-fold excess of unlabelled TAM(OH) or a 20-, 200- or 2000-fold excess of oestradiol 1 h before injection of [³H]TAM(OH). After injection of [³H]TAM(OH) or [³H]oestradiol, autoradiograms showed concentration of radioactivity in nuclei of stromal, epithelial and myometrial cells, but this labelling varied among the cell types depending upon which compound was injected. After [³H]TAM(OH) injection, the decreasing order of labelling intensity was stroma, myometrium, epithelium; after [³H]oestradiol injection the decreasing order was stroma, epithelium, myometrium. Injection of TAM(OH) before [³H]TAM(OH) eliminated nuclear labelling in all the uterine cell types. Injection of oestradiol before [³H]TAM(OH) decreased nuclear labelling and resulted in the concentration of label in the cytoplasm of luminal epithelium which was not present when [³H]TAM(OH) was injected alone. Cytoplasmic labelling increased initially as the oestradiol competition dose increased, but the increase in labelling did not continue with increasing concentrations of oestradiol. The results indicate that antioestrogen and oestrogen localize to nuclei of the same uterine cell types, but that cellular uptake differs among the tissue compartments. The results also suggest that a high concentration of antioestrogen-binding sites exist in the cytoplasm of the uterine luminal epithelium.     

Partial purification and characterization of oestrogen receptors in subfractions of hepatocyte plasma membranes

To assess the subcellular distribution of oestrogen-binding components in their native state, plasma membrane and other cell fractions were prepared from hepatocytes in the absence of [³H]oestradiol-17β. Cells from livers of ovariectomized rats were disrupted, with submaximal homogenization in buffered isotonic sucrose with CaCl₂ and proteinase inhibitor, and fractionated by using isotonic media. Fractions were characterized by determinations of enzyme activities, biochemical constituents and ligand binding. Specific binding of 2nm-[³H]oestradiol-17β to intact cells and their fractions was detemined after equilibration for 1.5h at 4°C. More than 92% of the radioactivity from representative preparations was verified as authentic oestradiol by thin-layer chromatography. Activities of plasma-membrane marker enzymes as well as binding sites for oestrogen and for wheat germ agglutinin were present principally in particulate fractions, rather than in 105000g-supernatant fractions. However, by using alternative homogenization procedures (i.e. hypotonic media), known to fragment and strip structural components, oestradiol-binding sites and activities of plasma-membrane marker enzymes were distributed predominantly into cytosol. By using the more conservative procedures, plasma membranes of low (ρ=1.13–1.16) and high (ρ=1.16–1.18) density were purified from crude nuclear fractions. A second low-density subfraction of plasma membrane was prepared from microsome-rich fractions. Activities of plasma-membrane marker enzymes were enriched to about 28 and four times that of the homogenate in plasma membranes of low and high density respectively. Binding sites for wheat germ agglutinin and oestradiol were concentrated in low-density plasma membranes to 46–63 times that of the homogenate. Specific binding of oestrogen in low-density plasma membranes purified from crude nuclei was saturable, with an apparent association constant of 3.5nm. At saturation, such oestradiol receptors corresponded to 526fmol/mg of membrane protein. A Hill plot showed a moderate degree of positive co-operativity in the interaction of hormone with plasma membranes. Specific binding of [³H]oestradiol-17β was reduced by a 200-fold molar excess of unlabelled oestradiol-17β, oestriol or diethylstilbestrol, but not by oestradiol-17α, cortisol, testosterone or progesterone. Binding was also blocked by prior exposure of membranes to trypsin or to 60°C, but remained essentially undiminished by extraction of membranes with either hypotonic or high-salt buffers. Extraction with 0.1% (v/v) Triton X-100 partially solubilized the oestrogen-binding component(s) of plasma membranes. Particle-free extracts were resolved on 5–20% (w/v) sucrose density gradients with either 0.01m- or 0.4m-KCl, and the fractions were analysed by adsorption to hydroxyapatite. In low-salt gradients macromolecule-bound oestrogen sedimented at predominantly 7.4S and binding was 1560 times that of the homogenate. Under high-salt conditions oestradiol-binding activity occurred at both 3.6S and 4.9S.     

Prolonged antioestrogenic activity of ICI 46, 474 in the ovariectomized mouse.

Subcutaneous administration of ICI 46,474 (3 mg) to ovariectomized mice was found to produce vaginal refractoriness to subcutaneously administered oestradiol for up to 6 weeks. Tritiated oestradiol-17 beta accumulated in the uterus and vagina of the ovariectomized mouse, with maximum accumulation at 3 to 4 hr. This property of the target tissues was used to investigate the binding of tritiated oestradiol after the administration of 3 mg ICI 46,474 to ovariectomized mice. Radioactivity in the vagina was found to be comparable to control values 6 weeks after ICI 46,474 administration; uterine levels of radioactivity returned to control values by 10 weeks. Administration of ICI 46,474 had an oestrogenic effect upon the mouse uterus whereas the vagina appeared to be initially stimulated and was then unable to respond to or to bind oestradiol.     

Cellular and subcellular localization of 3H-diethylstilboestrol in the central nervous system

Summary The cellular and subcellular localization of radioactivity in the brain of immature female rats was determined by dry-mount autoradiography 2 h after iv injection of 1.0 g of (monethyl-³H) diethylstilboestrol per 100 g body weight. A specific topographic pattern of nuclear concentration of the synthetic oestrogen was obtained similar to that for ³H-oestradiol-17 in specific neurons of the basal hypothalamus, preoptic region and amygdala. In competition experiments, the nuclear concentration of radioactivity in all areas studied was inhibited by unlabeled oestradiol, while unlabeled testosterone had no effect. These data suggest that although oestradiol can bind to androgen receptors, the oestrogen receptor itself can account for the localization seen after the injection of ³H-oestradiol.This research was supported in part by US PHS Grant No. NS12933NIH Career Development Awardee No. NS00164The expert technical assistance of Ms. Riki Ison and Ms. Linda Furr is gratefully acknowledged.     

Variations in the concentrations of androstenedione in peripheral plasma of women the day and during the menstrual cycle

The target tissues (e.g., hypothalamus, pituitary, uterus and vagina) of mature female ovariectomized rats show selective uptake of radioactivity in one hour after the injection of 6,7, ³H-estradiol-17β in a dose of 0.1 μg per 100 g body weight. Injection of 100 μg norethindrone or norgestrel per 100 g body weight 15 min before or 15 min after the administration of tritiated estradiol reduced the radioactivity in most target tissues, and also in the non-target tissues to a lesser extent. The uptake of radioactivity in the pituitary and uterus is reduced more by norethindrone than by norgestrel treatment when these Steroids were injected 15 min after estradiol-17β injection. It appears that there exists a competitive inhibition of estradiol-17β by these contraceptive Steroids in the rat. It is speculated that such competition with estradiol-17β may be an inherent property of the 17-substituted 19-nortestosterone group of Steroids.     

The rate of uptake of sex steroids from water by Tinca tinca is influenced by their affinity for sex steroid binding protein in plasma

Two experiments were carried out in which male and female tench Tinca tinca were placed in individual containers and tritiated steroids then added to the water. Water samples were collected over the next 6 or 7 h and the fish then sacrificed, bled and the gall bladder removed. Radioactivity was counted in all the samples. Over the course of the exposure period in the first experiment (7 h), radioactivity of 11‐ketotestosterone (11‐KT) in the water was depleted by 11%, 17,20β‐dihydroxypregn‐4‐en‐3‐one (17,20ß‐P) and 17,20α‐dihydroxypregn‐4‐en‐3‐one (17,20α‐P) by 28%, testosterone (T) by 56% and androstenedione (AD) by 68%. HPLC analysis of water samples at 3 h indicated that none of the steroids was extensively metabolized during the experiment. Females had a faster rate of uptake of AD than males. In the second experiment (6 h), radioactivity of cortisol in the water was depleted by 5%, 11‐KT by 7%, 17‐hydroxypregnen‐4‐ene (17‐P) by 17%, 17β‐oestradiol (E₂) by 35%, T by 37% and AD by 44%. In both experiments, the amounts of radioactivity that were recovered from the gall bladder and plasma were positively correlated with the rate of disappearance of radioactivity from the water. The ability of the steroids to bind to sex steroid binding protein (SBP) of tench plasma was tested by incubating plasma with radioactive steroids and then separating bound and free with ice cold dextran‐coated charcoal. When plasma at a final dilution of 1 : 60 (v/v) was incubated with 5 nM of each steroid, the percentage of radiolabel bound to SBP was: T 48% AD 44%, E₂ 30%, 17‐P 17%, 11‐KT 13·2%, 17,20α‐P 10·3%, 17,20β‐P 4·5% and cortisol 0%. Saturation analysis established dissociation constants (K_d; mean ± s .e .) of 3·4 ± 0·4, 2·2 ± 0·2, 4·0 ± 0·3. 9·0 ± 2·8 and 51·8 nM and binding capacities (B_max) of 201 ± 29, 201 ± 33, 165 ± 3, 187 ± 15 and 13·4 nM for T, AD, E₂,17‐P and 17,20β‐P respectively. The ability of steroids to displace tritiated T and AD from SBP was in the rank order AD > T > E₂ > 17,20αP = 17,20β‐P = 11‐KT = 17‐P > cortisol. Thus, the ability of tench plasma to bind certain steroids showed a relatively strong correlation with the ability of the fish to take up these steroids from water. Modelling of data for AD and 17,20β‐P helped to show why and how plasma binding had a strong influence on the rate of uptake (and hence release) of the steroids.     

Progesterone in the uterus. VII. Uptake of cortisol and incorporation of progesterone under simultaneous application of cortisol into rat uterus

After injection of radioactively labelled Cortisol, the distribution of the radioactivity in the subcellular fractions of the rat uterus (nuclei, mitochondria, microsomes and 105 000 × g supernatant) was studied. In all fractions, radioactivity was observed and maxima were found 10, 20 and 50 min. after injection of the labelled hormone. Radioactivity was measured in all subcellular fractions even 180 min. after application of labelled cortisol. Additionally, radiolabelled progesterone and unlabelled cortisol in the ratio 1:1 or 1:2 (moles:moles) were injected into the animals. Studying the uptake of labelled progesterone in the subcellular fractions of the uterine tissue, revealed that no competition of unlabelled cortisol could be observed 10, 20 and 50 min. after application of the hormone mixture, compared with the control experiments. The results of this study give evidence that the progesterone uptake into rat uterus is specific and cannot be influenced by unlabelled cortisol.     

Pituitary uptake of 125I-D-Leu6, Des-Gly N2(10) LH-RH-ethylamide in ovariectomized rats pretreated with oestradiol-17 beta.

The objective of this study was to determine if pretreatment of ovariectomized rats with oestradiol-17 beta affects the anterior pituitary uptake of 125I-D-Leu6, Des-Gly NH2(10)-LH-RH-ethylamide (125I-D-Leu6-LH-RH). Oestradiol-17 beta (0.5 microgram/0.5 ml oil) or oil was administered to ovariectomized rats at 2, 4, 8, 12, 16, 20 or 24 h before death, and at 30 min before death, 5 ng 125I-D-Leu6-LH-RH were injected intravenously. The serum LH response to analogue administration in oil-treated rats did not change over time, but that in oestradiol-treated rats was depressed for 4 h and restored 8-24 h after oestradiol treatment, with the greatest response being at 16 h. However, the pituitary (adrenal, CNS cortex and thyroid) uptake of 125I-D-Leu6-LH-RH in oestradiol-treated and control rats did not change over the 24-h time period. These data suggest that oestradiol-17 beta does not affect pituitary responsiveness to 125I-D-Leu6-LH-RH by inhibiting or facilitating the uptake of this analogue by the anterior pituitary.     

STUDIES ON THE LABELLING PATTERNS OF RNA FROM CEREBRAL CORTEX NUCLEI

RNA labelling patterns in nuclei from rat cerebral cortex were investigated subsequent to intracerebral injection of [³H]uridine. Although there was a rapid uptake of label into the ‘heavy’ regions when nuclear RNA was analysed in density gradients, it was not possible to show conclusive evidence for 455 ribosomal precursor RNA. Methyl-ation of 18S and 28S nuclear RNA became evident only after 2 hr and did not appear to involve the intermediacy of RNA species of higher molecular weight.     

Estrogen target cells in the pituitary of platyfish,Xiphophorus maculatus

Summary The distribution of estradiol-concentrating cells in the pituitary of the platyfish, Xiphophorus maculatus, is studied after the injection of ³H estradiol-17 by thaw-mount autoradiography. Autoradiograms prepared 2–8 h after the injection show nuclear concentration of radioactivity in certain cells of the proximal pars distalis, while no nuclear labeling is found in cells of the rostral pars distalis, pars intermedia and pars nervosa. Radioactively labeled cells are identified as gonadotropes by a combined technique of thaw-mount autoradiography and immunoperoxidase staining with antiserum to ovine LH. Approximately 80% of the immunoreactive LH cells show a concentration of radioactivity in their nuclei. These observations indicate that in teleosts, as in mammals, estradiol has a direct effect on pituitary gonadotropes.Supported by PHS grant NS09914. The authors are grateful to Dr. D.G. Humm for providing the platyfish     

Nuclear binding of oestradiol-17β and induction of protein synthesis in the rat uterus during postnatal development

1. The uterine response to a single injection of oestradiol-17beta during postnatal development of the rat was studied with respect to (i) nuclear binding of oestradiol-17beta; (ii) induction of the synthesis of a specific cytoplasmic protein (;induced protein' of Gorski); (iii) rate of incorporation of (3)H-labelled amino acids into total protein and into nuclear acid-soluble and acid-insoluble protein; and (iv) rate of [(3)H]thymidine incorporation into DNA. 2. Specific nuclear binding of oestradiol-17beta could be demonstrated even at birth. Administration of oestradiol-17beta in vivo caused a significant increase in the number of nuclear binding sites in rats aged 10 days or older. 3. A rapid method is described for the detection of the ;induced protein', based on cellulose acetate electrophoresis. Induction of this protein could be demonstrated at the age of 10, 15 and 20 days, but not in 5-day-old rats. 4. In 20-day-old rats the rate of (3)H-labelled amino acid incorporation into protein increased by 3h after oestradiol administration. Incorporation into the different protein fractions reached peak values asynchronously: at 3-4h for acid-insoluble nuclear protein, at 6h for total protein and at about 12h for acid-soluble protein. 5. Treatment with oestradiol failed to stimulate amino acid incorporation into protein in 5- or 10-day-old rats; at the age of 15 to 30 days the hormone caused a significant increase in incorporation into total protein and into both types of nuclear protein. 6. Since the capacity for nuclear binding of oestradiol and for synthesis of the induced protein is demonstrable in the rat uterus before it acquires the ability to respond to the hormone with enhanced general protein synthesis and DNA synthesis, it appears that nuclear binding and the synthesis of the induced protein may be necessary but not sufficient conditions for the trophic action of oestradiol.     

Oestradiol uptake and retention, and high-affinity binding sites in cultured rabbit uterus

Oestradiol uptake and turnover was examined in rabbit uterus maintained in organ culture for up to 3 days. Serum decreased the uptake of [(3)H]oestradiol, whereas insulin had no significant effect. During the first 24h of culture unoccupied high-affinity receptors for oestradiol were markedly depleted in the cytosol. Nuclear binding sites remained high during the first day of culture, and were still present after 3 days. The stability of nuclear-bound oestradiol was confirmed by examining the turnover of radioactivity during culture of uteri of rabbits injected with [(3)H]oestradiol 6h before death. Over half of the radioactivity was retained for as long as 3 days in tissue cultured in the absence of oestrogen. In tissue cultured for 24h with unlabelled oestrogen, there was a progressive increase in the displacement of [(3)H]oestradiol as the concentration of unlabelled hormone in the medium was increased from 0.1 to 5nm. Higher concentrations of oestradiol had little additional effect. The oestradiol involved in this displacement reaction was associated with macromolecules, characterized by Sephadex G-25 chromatography and sucrose-density-gradient ultracentrifugation of the 0.4m-KCl extract of the nuclear pellet.     

OESTROGEN EFFECTS ON BRAIN AND PITUITARY ENZYME ACTIVITIES

Abstract— Ovariectomized female rats were treated daily with oestradiol-17β benzoate for intervals up to one week and enzyme activities were measured in the pituitary and various brain regions. Brain regions were selected for study on the basis of their previously demonstrated content of putative oestradiol receptor sites. (1) Pituitary showed oestrogen-dependent increases in glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and lactic dehydrogenase (LDH), and no change in NADP⁺-dependent isocitric dehydrogenase (ICDH), NADP⁺-dependent malic dehydrogenase (MDH) or hexokinase (HK). MDH and ICDH were elevated in whole hypothalamus. Enzyme activities did not change significantly in whole amygdala, cerebral cortex, or hippocampus. (2) Sub-regions of the preoptic area, hypothalamus and amygdala were dissected to obtain more highly concentrated populations of cells containing putative oestrogen receptor sites. In the basomedial sub-region of hypothalamus, activities of MDH, ICDH and G6PDH were elevated by oestrogen treatment. In the corticomedial sub-region of amygdala, MDH and ICDH were elevated by oestrogen treatment. No change was observed in any of the six enzymes in medial preoptic area. (3) Increases in enzyme activities were related to the total in vivo dose of oestradiol benzoate given. (4) Hypophysectomy or adrenalectomy did not prevent the enzymatic responses to oestrogen. (S) Oestrogen added directly to the enzyme incubation medium did not change enzyme activities. (6) Weight loss in ovariectomized rats due to reduced food intake did not increase enzyme activities. (7) In the pituitary, good correlation was obtained between the known receptor binding properties of various oestrogenic and non-oestrogenic steroids and the elevation in G6PDH activity. The results indicate that oestradiol acts directly to cause changes in activities of some brain and pituitary enzymes. The possibility is discussed that these changes may result from oestrogen interaction with putative receptor sites found in pituitary and certain brain regions.     

The uptake of radioactivity by the uterus of the rabbit following the sytemic administration of (3H) estradiol-17beta and (3H) estrone and the identification and subcellular localization of radiometabolites in the uterus

In an effort to determine the relevance of the uterine oxido-reduction of estrogens to their action in the rabbit uterus, the uterine uptake of radioactivity administered subcutaneously as [³h] estradiol-17β or [³H]estrone and the subcellular distribution of radio-metabolites in the uterine tissue were studied. The animals were killed 20 min, 1, 3 and 9 hr after the administration of 0.1 μg tritiated steroid and the relative proportions of radioactive estradiol-17β and estrone in plasma and in ‘cytosol’, ‘mitochondrial/microsomal’ and ‘nuclear’ fractions of the uterine homogenates were studied. Despite the presence of a high proportion of estrone in chloroform extract of plasma, very little was found in the fractions from uterine tissue irrespective of the steroid administered. Highest levels of uterine estrone were found in the ‘mitochondrial/microsomal’ preparation. There was no apparent difference in the pattern of uptake of radioactivity administered as [³H] estradiol-17β or [³H] estrone. The presence of high levels of 17β-hydroxysteroid dehydrogenase activity in the rabbit uterus may be responsible for the apparent difference between these results and those of similar experiments using the rat.     

High-affinity binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin in cell nuclei from rat liver

The intranuclear binding of radioactive 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rat liver has been studied both in vivo and in vitro. Following the intravenous administration of [1,6-³H]TCDD, a maximum uptake by cell nuclei could be observed at 2 h after injection with a concurrent decrease in the cytosolic uptake. Using linear sucrose density gradient centrifugation, dextran-coated charcoal adsorption assay, DEAE-Sepharose ion-exchange chromatography, competition, enzymatic and saturation studies, a high-affinity binding protein for TCDD in liver cell nuclei could be demonstrated both in vivo and after an exchange in vitro of intravenously administered unlabelled 2,3,7,8- tetrachlorodibenzofuran (TCDBF) for [³H]TCDD. Sucrose density gradient analysis showed a size of 4–5 S for both the cytosolic and nuclear TCDD binding entity. The specific binding of [³H]TCDD to nuclear components was heat labile and saturable and had an equilibrium dissociation constant of 1.05 nM. Based on a differential susceptibility to specific hydrolases, i.e. DNAase, RNAase, trypsin and pronase, the binding entity appears to be a 4–5 S salt-extractable protein.     

The effects of copper, iron and zinc on digestive enzyme activity in the hybrid tilapia Oreochromis niloticus (L.) ×Oreochromis aureus (Steindachner)

The present experiment was conducted to study effects of Cu, Fe and Zn on activities of digestive enzymes of the hybrid tilapia Oreochromis niloticus×Oreochromis aureus. The acidic protease activities increased 65·5 and 55·1% by addition of homogenates of digesta‐containing stomach with copper (75 mg l⁻¹) and zinc (50 mg l⁻¹) respectively. Addition of Cu and Zn increased the activities of protease in the hepatopancreas homogenates by 132·7 and 38·1% respectively, and reduced the activity of protease in the digesta‐containing intestine homogenates by 11·0 and 13·8% respectively. Addition of Fe (50 mg l⁻¹) increased the acidic protease activity by 96·7% but did not alter the activities of protease in the intestine and hepatopancreas. Addition of Cu markedly inhibited activities of amylase in intestine and hepatopancreas homogenates, while Zn addition showed no effects. Addition of Fe reduced activities of amylase in the intestine homogenates by 47·9% but had no effect on amylase activities in the hepatopancreas. When Cu (75 mg kg⁻¹), Fe (50 mg kg⁻¹) and Zn (50 mg kg⁻¹) were supplemented to basal diet for 3 weeks, the activities of amylase in hepatopancreas homogenates increased 125·3, 215·6 and 70·0%, respectively, the activities of amylase in intestine increased 79·8, 74·6 and 48·5%, respectively, and the activities of lipase in intestine increased 90·5, 149·8 and 84·0%, respectively. Supplementation of Cu, Fe or Zn into diet had no effects on activity of protease in all digestive organs. Therefore, the results suggest that effects of Cu, Fe and Zn on activity of digestive enzymes in vitro were different from those seen in vivo, and that the positive effects of Cu, Fe and Zn supplemented to fish diet would be valuable information for formulating fish feed.     

The action of high doses of oestradiol on implantation and decidual reaction in the rat

The action of high doses of oestradiol on ovum implantation and decidual reaction was studied in pseudo-pregnant rats. It is shown that anomalies of ovum implantation take place after the injection of 10 μg of oestradiol on the 4th day of pregnancy, in that the decidual reaction is inhibited as demonstrated by ponderal evolution, lower ³H uridine uptake, ultrastructural features and the ploidy level of stromal cell nuclei.     

Analysis of the membrane-associated poly(A)+RNA in the cytoplasm of dormant Artemia cysts by DNA excess hybridization: Evidence for a nuclear origin

Encysted embryos of Artemia contain latent mRNA, to a large extent associated with a fraction of cytoplasmic membranes. The membranes, purified by EDTA treatment and banding in a sucrose gradient at 1.17 g/cm³, include endoplasmic vesicles and mitochondria. The origin of the membrane-associated poly(A)⁺RNA was therefore investigated. In gel electrophoresis poly(A)⁺RNA from the purified membranes of dormant cysts forms two distinct bands at approx. 3·10⁵ and 5·10⁵ Da. Later during development the lighter component decreases. Nuclei from dormant cysts are devoid of poly(A)⁺RNA, while nuclei from developing embryos (50% emergence) contain a predominant poly(A)⁺RNA component of approx. 5·10⁵ Da. ¹²⁵I-labelled preparations of nuclear DNA and of nuclear and membrane-associated poly(A)⁺RNA were used in reassociation and hybridization experiments with excess nuclear DNA. Poly(A)⁺RNA from the membranes of dormant cysts hybridized to nuclear DNA to the same extent as the nuclear poly(A)⁺RNA from developing embryos. The hybridization of labelled, nuclear poly(A)⁺RNA to nuclear DNA was strongly inhibited by unlabelled membrane RNA from either dormant cysts or developing embryos. It is concluded that the stored, membrane-associated poly(A)⁺RNA in dormant cysts is essentially of nuclear origin. The 5·10⁵-Da component is largely homologous with the corresponding component of nuclear poly(A)⁺RNA at later stages.     

Oestradiol inhibits the insulin secretion on the first day of treatment in the ovariectomized rat

Long term oestradiol treatments stimulate the B cell of the endocrine pancreas. The first effects of oestradiol-17-beta were studied in ovariectomized rats, 16 hours after a subcutaneous injection of various concentrations of this hormone (0, 2.5, 25, 50 micrograms). Plasma oestradiol concentrations, food intake and insulin secretion from islets of Langerhans were measured. Oestradiol always decreased food intake and insulin secretion. However, this inhibiting effect of oestradiol on the B cell was also found in fasted rats. This negative action did not appear on basal insulin secretion but on glucose-induced insulin response. It was characterized by a decrease in the B cell capacity of response to glucose. Short and long term opposite actions of oestradiol on the B cell of the endocrine pancreas could be compared to similar effects shown with glucocorticoids.     

Progestagen-concentrating cells in the brain, uterus, vagina and mammary glands of the galago (Galago senegalensis)

Progestagen-concentrating cells were localized in the oestrogen-primed ovariectomized galago by radioautography after injection of [3H]promegestone (R5020). In the brain, radioactivity was concentrated in the nuclei of neurones in the preoptic region and in the mediobasal hypothalamus. Labelled cells were also observed in the anterior pituitary. In the uterus (uterine horns and cervix), the muscle and stromal cells showed greater labelling than did the glandular and luminal epithelia. Labelled cells were present in the different cell layers of the vagina. The majority of glandular epithelial cells of the mammary glands exhibited a high degree of labelling. Pretreatment with an excess of unlabelled promegestone but not with an excess of nonradioactive testosterone reduced the nuclear concentration of radioactivity in these target tissues. These results show that there are no major differences in the distribution of progestagen-concentrating cells in rodents and galago.