Tamoxifen decreases the estradiol induced progesterone receptors by interfering with nuclear estrogen receptor accumulation

The retention time of the estrogen receptor in the nucleus of target cells after antiestrogen treatment has been shown to be longer than after estradiol. This paper describes the accumulation of nuclear estrogen receptors and the obtention of estrogenic responses (i.e. synthesis of cytosolic progesterone receptors and DNA) in the rat uterus after tamoxifen treatment in the presence or absence of estradiol. One-week ovariectomized adult rats were implanted with a silicone elastomer capsule containing corn oil or 25 micrograms estradiol/capsule (0 h). 48 h after implantation rats were injected with corn oil or 2 mg tamoxifen/kg and decapitated at 72, 96 or 120 h after implantation. In parallel experiments the implants were removed just before the injections of tamoxifen or oil. Tamoxifen injected into rats implanted with oil increased both the occupied nuclear receptors and the progesterone receptors at 96 h. In rats implanted with estradiol, tamoxifen did not increase the occupied nuclear receptors and decreased the levels of progesterone receptor and DNA at 96 h. In rats whose estradiol implants were removed at 48 h tamoxifen did not change the level of occupied nuclear receptors at 72 h but it increased them abruptly at 96 and 120 h. In these rats progesterone receptors decreased at 72 h but they increased at 96 and 120 h, and DNA decreased at 120 h to a lower level than before implantation. The results suggest that when estradiol is acting, tamoxifen is not able to increase the level of occupied estrogen receptor and it acts as an antiestrogen by decreasing the high level of progesterone receptors previously induced by estradiol. When estradiol is not acting tamoxifen behaves as a partial estrogen agonist by inducing progesterone receptors. However, the antiestrogenic action of tamoxifen on the rat uterus DNA does not seem to be affected by estradiol.     

Oleoyl-estrone induces the massive loss of body weight in Zucker fa/fa rats fed a high-energy hyperlipidic diet

To test whether oleoyl-estrone plus a hyperlipidic diet affects body weight in Zucker fa/fa rats, 13-week-old male Zucker obese (fa/fa) rats initially weighing 440-470 g were used. They were fed for 15 days with a powdered hyperlipidic diet (16.97 MJ/kg metabolizable energy) in which 46.6% was lipid-derived and 16.1% was protein-derived energy and containing 1.23 +/- 0.39 μmol/kg of fatty-acyl esters of estrone. This diet was supplemented with added oleoyl-estrone to produce a diet with 33.3 μmol/kg of fatty-acyl estrone. Oral administration of oleoyl-estrone in a hyperlipidic diet (at a mean dose of 0.5 μmol. kg(-1).d(-1)) resulted in significant losses of fat, energy and, ultimately, weight. Treatment induced the maintenance of energy expenditure combined with lower food intake, creating an energy gap that was filled with internal fat stores while preserving body protein, in contrast with the marked growth of controls fed the hyperlipidic diet. Treatment of genetically obese rats with a hyperlipidic diet containing additional oleoyl-estrone resulted in the loss of fat reserves with scant modification of other metabolic parameters, except for lower plasma glucose and insulin levels. The results agree with the postulated role of oleoyl-estrone as a ponderostat signal.     

Effects of oral estrone on rat energy balance

Oral doses of estrone from 10 nmol/(kg day) to 10 micromol/(kg day) were given to adult Wistar male rats for 10 days. Body composition, energy balance, total body estrone balance and plasma metabolites and hormones were measured at the end of the treatment. Body weight (as well as food intake, body energy, fat and water accrual) increased at doses in the 10--100 nmol/(kg day) range, but decreased at higher doses. Energy expenditure decreased with increasing doses of estrone. Plasma metabolite changes suggested the maintenance of energy homeostasis, and lipid parameters indicated that lipid mobilization increased with the increasing doses of estrone. Plasma estrone, acyl-estrone and estradiol levels decreased at low doses and increased at high doses of estrone. We conclude that: (a) repeated estrone gavages, even at very high doses, do not result in the accrual of estrone in the body; (b) low doses of estrone promote growth and high doses decrease body mass and fat accretion; (c) administration of estrone at low doses decreases its circulating levels and the levels of estradiol and acyl-estrone, a situation reverted at higher doses and (d) estrone administration induces a dose-dependent shift towards lower energy expenditure.     

Differential Short-Term Distribution of Estrone and Oleoyl-Estrone Administered in Liposomes to Lean and Obese Zucker Rats

Thirteen-week-old female Zucker lean (Fa/Fa) and obese (fa/fa) rats were injected through a cannula inserted in the left jugular vein with 1 mL/kg of ³H-labeled oleoyl-estrone in liposomes (Merlin-2) (i.e., 670 fmol, 84 kBq). The rats were killed 10 minutes later and dissected. The presence of intact or hydrolyzed oleoyl-estrone was later determined in all samples. The pattern of distribution of estrone was quite different from that of oleoyl-estrone both in rats that were lean and in those that were obese. Estrone was better retained by white adipose tissue than oleoyl-estrone. Liver, spleen, and lungs accumulated more oleoyl-estrone and split part of it, from 4.7% (lung, obese) to 27% (liver, lean). The overall high retention of estrone by the rat tissues results in its very low circulating levels. The fast splitting of liposome-carried oleoyl-estrone by most tissues (up to more than 67% by intestine and skin of lean rats) may help explain the rise in blood free estrone. The differences between lean and obese Zucker rats are mainly quantitative in the case of estrone, the main differences being found in blood and adipose tissues. However, when we compare the data for oleoyl-estrone, the differences cannot be dismissed simply as due to differences in body size or the extent of fat deposits. A large portion of the label remained in the blood of the rats that were obese but not in those that were lean, the tissues of which took up more label. Brown adipose tissue shows a fair affinity for oleoyl-estrone in the rats that were lean but practically does not retain label in the rats that were obese, suggesting that oleoyl-estrone may have a direct effect on brown adipose tissue. The decreased uptake of oleoyl-estrone in rats that were obese shows that the mechanism regulating the turnover or disposal of this signal is altered in this type of genetic obesity.     

Daily Oral Oleoyl‐Estrone Gavage Induces a Dose‐Dependent Loss of Fat in Wistar Rats

Objective: To establish whether single daily oral doses of oleoyl‐estrone result in dose‐dependent slimming effects on normal weight rats, and to determine the changes in energy parameters induced by this treatment. Research Methods and Procedures: The effects of a daily oral gavage of oleoyl‐estrone (0, 0.2, 0.5, 1, 2, 5, 10, and 20 μmol/kg per day) in 0.2 ml of sunflower oil given over a 10‐day period were studied in groups, each of which contained six adult female Wistar rats initially weighing 190 to 230 g. A group of intact control rats receiving no gavage was included for comparison. Body weight and food intake were measured daily. Rats were killed on day 10 of treatment, and body composition (protein nitrogen, lipids, and water), liver lipids, and plasma parameters (glucose, triacylglycerols, total cholesterol, free fatty acids, 3‐hydroxybutyrate, urea, aspartate, alanine transaminases, insulin, leptin, and free and acyl‐estrone) were measured. Results: The administration of oleoyl‐estrone resulted in a dose‐dependent loss of body fat, because of a partly maintained energy expenditure combined with decreased food intake. The differences in the energy budget were met by internal fat pools. The changes recorded did not affect the levels of the main plasma energy homeostasis indicators: unaltered glucose, triacylglycerols, free fatty acids, 3hydroxybutyrate, and urea. Protein was accrued even under conditions of severe lipid store drainage. There were no changes in transaminases. No lipid accumulation was recorded in the liver. Plasma insulin and leptin levels decreased with increased oleoyl‐estrone doses, whereas the levels of free and esterified estrone increased with treatment, although not in proportion to the dose received. Discussion: Oral treatment with oleoyl‐estrone resulted in the specific dose‐related loss of fat reserves with little change to other metabolic parameters. These results agree with the postulated role of oleoyl‐estrone as a ponderostat signal.     

Oleoyl-estrone does not have direct estrogenic effects on rats

The estrogenic effects of oleoyl-estrone (OE) administration, either though continuous i.v. infusion with osmotic minipumps or administered by daily oral gavage, were studied. Binding of OE to human recombinant purified alpha receptors was negligible, and that of estrone (E1) was only a fraction of 17beta-estradiol (E2) binding. Intravenous--but not oral--OE administration resulted in marked increases of both E1 and E2 in rat plasma, but oral OE did not induce significant changes in either plasma hormone in Wistar or Zucker rats. The weight of uteri and ovaries increased with time of administration in Zucker rats treated with i.v. OE, but inguinal mammary gland proliferation between subcutaneous adipose tissue was even more marked. Oral administration of OE, however, did not increase either uterine weight or mammary gland proliferation, even at doses (10 micromol/kg x d) higher than those given i.v. (3.5 micromol/kg x d). The results indicate that i.v. administration of OE resulted in limited estrogenic effects mainly due to the high accumulation of E1 giving rise to significant increases in E2. On the other hand, oral administration of OE, even at higher daily doses, did not increase the circulating levels of either estrogen and, therefore, there were no significant effects on mammary gland proliferation or uterine weight. The oral administration of OE as a slimming drug, then, do not result in estrogenic side effects over a wide range of daily doses.     

Tamoxifen produces conditioned taste avoidance in male rats: An analysis of microstructural licking patterns and taste reactivity

Estrogen receptor activation has been shown to reduce body weight and produce a conditioned reduction in food intake in male rats that is putatively mediated by estradiol's suggested aversive effects. Evidence has shown that the selective estrogen receptor modulator tamoxifen used in the prevention and treatment of breast cancer may also produce changes in food intake and body weight, which are known to impact cancer development and survival. The purpose of the present study was to examine whether tamoxifen produces a conditioned reduction in intake similar to estradiol by producing a conditioned aversion. A one bottle lickometer test was used to examine conditioned changes in sucrose drinking, while the taste reactivity test was used to measure rejection reactions, which serve to index aversion in rats. A backward conditioning procedure that consisted of 3 conditioning days and one vehicle test day was used to examine conditioned changes in 0.3 M sucrose intake and taste reactivity. Our results show that tamoxifen produced a conditioned reduction in sucrose drinking in a one bottle fluid intake test that was similar to the effects produced by estradiol (positive control); however, no active rejection reactions were produced by either tamoxifen (1 and 10 mg/kg) or estradiol. The present results suggest that tamoxifen, at the doses used in the present study, acts as an estrogen receptor agonist to regulate food intake and that the conditioned reduction in intake produced by tamoxifen and estradiol reflects conditioned taste avoidance rather than conditioned taste aversion.     

Oleoyl-estrone is a precursor of an estrone-derived ponderostat signal

Oleoyl-estrone (OE) is a powerful anti-obesity compound that decreases food intake, decreases insulin resistance and circulating cholesterol. OE stimulates a severe loss of body fat by decreasing adipose tissue lipid synthesis and maintaining lipolysis. Therefore, the body economy loses lipid energy because energy expenditure is maintained. This study analyses the discrepancy between OE effects and the distribution of labelled OE in plasma. Estrone radioimmunoassay of organic solvent plasma extracts of rats treated with OE showed the massive presence of acyl-estrone, but saponification did not release estrone, but containing similar unknown compound. Analysis of label distribution in plasma after oral gavages of (3)H-OE showed the presence of a more hydrophilic compound than OE or any estrogen as well as (3)H(2)O, formed from (3)H-OE in the acidic stomach medium. OE was not attached to a specific transporter in plasma. Through serum HPLC analysis we found W, a labelled derivative more hydrophilic than OE or estrone. The results were confirmed using (14)C-OE. HPLC-MS/MS studies showed that plasma OE levels were one order of magnitude lower than those of W. When liver cell cytosols from rats laden with (3)H-OE were incubated with nuclei from untreated rats, the OE-derived label (i.e., Ws) was found attached to nuclear DNA. Neither estradiol nor estrone interfered with its binding. W is a fairly hydrophilic compound of low molecular weight containing the estrone nucleus, but it is not an ester because saponification or esterases do not yield estrone as OE does. It is concluded that OE acts through its conversion to W, its active form; which binds to a nuclear receptor different from that of estrogen. The estimated W serum levels are proportional to the pharmacological OE effects in vivo. We postulate W as a new type of hormone that exerts the full range of in vivo effects thus far attributed to OE. The full identification of W is anticipated to open the way for the development of new OE-like anti-obesity drugs.     

Selective estrogen receptor modulators protect hippocampal neurons from kainic acid excitotoxicity: differences with the effect of estradiol

Neuroprotective effects of estradiol are well characterized in animal experimental models. However, in humans, the outcome of estrogen treatment for cognitive function and neurological diseases is very controversial. Selective estrogen receptor modulators (SERMs) may represent an alternative to estrogen for the treatment or the prevention of neurodegenerative disorders. SERMs interact with the estrogen receptors and have tissue-specific effects distinct from those of estradiol, acting as estrogen agonists in some tissues and as antagonists in others. In this study we have assessed the effect of tamoxifen, raloxifene, lasofoxifene (CP-336,156), bazedoxifene (TSE-424), and 17beta-estradiol on the hippocampus of adult ovariectomized rats, after the administration of the excitotoxin kainic acid. Administration of kainic acid induced the expression of vimentin in reactive astroglia and a significant neuronal loss in the hilus. SERMs did not affect vimentin immunoreactivity in the hilus, while 17beta-estradiol significantly reduced the surface density of vimentin immunoreactive profiles. Estradiol, tamoxifen (0.4-2 mg/kg), raloxifene (0.4-2 mg/kg), and bazedoxifene (2 mg/kg) prevented neuronal loss in the hilus after the administration of kainic acid. Lasofoxifene (0.4-2 mg/kg) was not neuroprotective. These findings indicate that SERMs present different dose-dependent neuroprotective effects. Furthermore, the mechanisms of neuroprotection by SERMs and estradiol are not identical, because SERMs do not significantly affect reactive gliosis while neuroprotection by estradiol is associated with a strong down-regulation of reactive astroglia.     

Estrogen receptor ligands counteract cognitive deficits caused by androgen deprivation in male rats

Androgen deprivation causes impairment of cognitive tasks in rodents and humans, and this deficit can be reverted by androgen replacement therapy. Part of the effects of androgens in the male may be mediated by their local metabolism to estradiol or 3-alpha androstanediol within the brain and the consequent activation of estrogen receptors. In this study we have assessed whether the administration of estradiol benzoate, the estrogen receptor β selective agonist diarylpropionitrile or the estrogen receptor α selective agonist propyl pyrazole triol affect performance of androgen-deprived male Wistar rats in the cross-maze test. In addition, we tested the effect of raloxifene and tamoxifen, two selective estrogen receptor modulators used in clinical practice. The behavior of the rats was assessed 2 weeks after orchidectomy or sham surgery. Orchidectomy impaired acquisition in the cross-maze test. Estradiol benzoate and the selective estrogen receptor β agonist significantly improved acquisition in the cross-maze test compared to orchidectomized animals injected with vehicle. Raloxifene and tamoxifen at a dose of 1 mg/kg, but not at doses of 0.5 or 2 mg/kg, also improved acquisition of orchidectomized animals. Our findings suggest that estrogenic compounds with affinity for estrogen receptor β and selective estrogen receptor modulators, such as raloxifene and tamoxifen, may represent good candidates to promote cognitive performance in androgen-deprived males.     

Effect of oral oleoyl-estrone on the energy balance of diabetic rats.

We studied the effects of a 10-day oral 10 micromol/kg oleoyl-estrone (OE) treatment on streptozotocin-diabetic Wistar, Goto-Kakizaki and control Wistar rats. Streptozotocin rats lost more than half the energy ingested as urine glucose. Oleoyl-estrone induced the loss of body weight (mainly body fat) in all groups. Energy expenditure was similar in the three groups of rats studied. Water turnover was deranged in streptozotocin rats, which spent 14% of energy available heating the water drunk. Body lipids were highest in Goto-Kakizaki; lipid levels in streptozotocin rats were very low. Oleoyl-estrone decreased body lipid content in Wistar and Goto-Kakizaki; oleoyl-estrone decreased triacylglycerols (44% in Wistar and Goto-Kakizaki and 22% in streptozotocin rats) and phospholipids but did not affect body cholesterol. Oleoyl-estrone decreased insulin and leptin, did not affect blood glucose but decreased plasma glucose in all groups. There were no changes in plasma triacylglycerols or fatty acids, but HDL, LDL and cholesterol decreased in all groups. The same effects of OE on insulin, plasma (but not blood) glucose and leptin were observed in both models, but the presence of insulin seems to be needed for OE to normalise glycaemia and to facilitate the uptake and utilisation of glucose by tissues. This different handling of glucose and triacylglycerol energy accounts for the disparate effects of OE on energy balance. The main conclusion of this study is that OE function as a lipid-mobilising hormone is dependent on the mass of reserves available, which in turn is closely related to insulin status. Lack of insulin thus results in limited OE effects, and insulin resistance does not prevent or limit the effects of OE on energy homeostasis or the mobilisation of fat.     

The influence of estrogen on hepatic cholesterol metabolism and biliary lipid secretion in rats fed fish oil

Both estrogen and dietary n-3 polyunsaturated fatty acids are known to be hypocholesterolemic, but appear to exert their effects by different mechanisms. In this study, the interaction between dietary fish oil (rich in n-3 polyunsaturated fatty acids) and estrogen in the regulation of hepatic cholesterol metabolism and biliary lipid secretion in rats was studied. Rats fed a low fat or a fish oil-supplemented diet for 21 days were injected with 17alpha-ethinyl estradiol (5 mg/kg body weight) or the vehicle only (control rats) once per day for 3 consecutive days. Estrogen-treatment led to a marked reduction in plasma cholesterol levels in fish oil-fed rats, which was greater than that observed with either estrogen or dietary fish oil alone. The expression of mRNA for cholesterol 7alpha-hydroxylase was decreased by estrogen in rats fed a low fat or a fish oil-supplemented diet, while the output of cholesterol (micromol/h/kg b.wt.) in the bile was unchanged in both groups. Cholesterol levels in the liver were increased by estrogen in rats given either diet, but there was a significant shift from cholesterol esterification to cholesteryl ester hydrolysis only in the fish oil-fed animals. Estrogen increased the concentration of cholesterol (micromol/ml) in the bile in rats fed the fish oil, but not the low fat diet. However, the cholesterol saturation index was unaffected. The output and concentration of total bile acid was also unaffected, but changes in the distribution of the individual bile acids were observed with estrogen treatment in both low fat and fish oil-fed groups. These results show that interaction between estrogen-treatment and dietary n-3 polyunsaturated fatty acids causes changes in hepatic cholesterol metabolism and biliary lipid secretion in rats, but does not increase the excretion of cholesterol from the body.     

Tamoxifen and raloxifene produce conditioned taste avoidance in female rats: A microstructural analysis of licking patterns

AimsEstrogen receptor activation has been shown to reduce body weight and produce conditioned taste avoidance (CTA) when estradiol administration is paired with a novel tastant. This study determined if the selective estrogen receptor modulators tamoxifen and raloxifene, which effectively prevent and treat breast cancer, can induce a CTA and alter body weight in ovariectomized (OVX)-female rats.Main methodsDuring conditioning, OVX-female rats were injected with tamoxifen, raloxifene, 17β-estradiol or vehicle, or were uninjected, prior to drinking 0.3 M sucrose in a lickometer. Immediately following sucrose access, alterations in locomotor activity and thigmotaxis (anxiety) were assessed in an open field apparatus. Conditioned drug effects on drinking, locomotor activity and anxiety were examined on a separate test day.Key findingsOur results suggest that both tamoxifen and raloxifene produce CTA that is similar to that produced by estradiol. Both the number and size of bursts of licking were significantly reduced, as well as body weight gain, in OVX-female rats treated with tamoxifen or raloxifene.SignificanceThe results of the present study suggest that tamoxifen and raloxifene may have the potential to produce CTA in breast cancer patients receiving chemoprevention care.     

Complex estrogenic regulation of catechol-O-methyltransferase (COMT) in rats

Catechol-O-methyltransferase (COMT) activity depends on gender, age and physiological status suggesting that estrogen may regulate COMT activity. In fact, estrogens down-regulate the function of COMT promoters in cell cultures. On the other hand, COMT may play an important role in estrogen-induced cancers due to its ability to inactivate estrogen metabolites and thereby lowering the levels of these potential carcinogens. In this study, we explored the effect of estrogen on COMT activity in vivo in rats. Male and female Wistar rats received 14-day treatments with either estradiol (100 μg/kg/day; s.c.) or tamoxifen (500 μg/kg/day; s.c.), respectively; in addition ovariectomized rats were studied. COMT activity and COMT protein expression were measured from various brain- and peripheral tissues. Although we found a regulatory function of estrogen, its effects were sex and tissue dependent. Antagonizing the effects of estrogen via tamoxifen increased COMT protein expression in several central and peripheral tissues. However, amounts of COMT protein and COMT activities did not always match. Generally, COMT activities were quite resistant to the effects of tamoxifen and estradiol. Estradiol, unexpectedly, doubled the amount of COMT protein in the prostate but exhibited down-regulatory function in the prefrontal cortex and kidneys. Ovariectomy by itself, however, had only minor effects on COMT activity and expression. It is noteworthy that the estrogen down-regulation and tamoxifen up-regulation of COMT were best substantiated in the prefrontal cortex and kidneys where COMT is physiologically important for dopamine metabolism.     

Oleoyl-estrone lowers the body weight of both ob/ob and db/db mice.

Homozygous obese db/db (BKS-Lepr(db) and ob/ob (B6-Lep(ob)) mice were treated for 14 days with a continuous infusion of a fat emulsion (controls) or loaded with oleoyl-estrone at doses of 12.5 and 50 nmol/g x d using surgically inserted osmotic minipumps. Treatment with oleoyl-estrone resulted in a marked decrease in body weight in both strains, compared with the unchecked growth of controls. In db/db mice, plasma urea and insulin, as well as liver lipid decreased with treatment. In ob/ob mice, the effect on insulin was more marked, in parallel with higher plasma lipids pointing to increased fat mobilisation. The results suggest that oleoyl-estrone effects on body fat reserves and insulin resistance are not mediated by leptin, since ob/ob mice lack this hormone and in the db/db it is present but cannot induce effects because of defective leptin receptors; in both cases oleoyl-estrone treatment lowers body weight.     

Distribution of oleoyl-estrone in rat plasma lipoproteins.

Pooled adult normal rat plasma was used for the separation of lipoprotein fractions: VLDL, LDL and HDL, from which a total lipids extract was obtained. The presence of fragments with the MW of estrone and oleoyl-estrone in the lipoprotein fractions was analyzed by HPLC-MS. The results show that oleoyl-estrone is the major estrone component in lipoproteins; this molecular species was present in all three lipoprotein lipid extracts. The lipoprotein fractions were used for the analysis of protein and lipid classes: triacylglycerols, total and esterified cholesterol and phospholipids as well as acyl-estrone. About half of the total acyl-estrone was in the HDL fraction and only about 10% in the VLDL fraction. HDLs contained about one molecule in 50 particles, LDLs one molecule per particle and VLDLs 15 molecules per particle, i.e. given their size, the larger lipoproteins contained more oleoyl-estrone than the HDLs. The distribution of this hormone suggests that oleoyl-estrone is lost with other lipids as the lipoproteins shrink. The results presented show that oleoyl-estrone is a molecule found naturally in rat lipoproteins in low concentrations - the lowest in HDLs - that are consistent with its postulated role in the control of body weight.     

Short-term treatment with estrone oleate in liposomes (Merlin-2) does not affect the expression of the ob gene in Zucker obese rats

Young female Zucker fa/fa rats of 370-430 g were implanted with osmotic minipumps releasing 3.5 mol/dayúkg of estrone oleate in liposomes (Merlin-2) into the bloodstream for up to 14 days. Merlin-2 induced a sustained loss of appetite, and a decrease in body weight of 3.5%, which contrasts with the 8.2% increase in controls during the period studied. Plasma insulin, glucose and urea decreased, and liver glycogen increased with Merlin-2 treatment. Plasma ACTH and corticosterone increased to a maximum at the end of the experiment. The expression of the ob gene in adipose tissue was unchanged, and plasma leptin levels were also unchanged by treatment. Estrone levels increased more than 1500-fold, and estrone oleate rose 100-fold during treatment. The fact that estrone oleate had no effect on the leptin levels or expression in obese rats, in contrast with the marked inhibition observed in the lean suggests that the functionality of the leptin receptor is essential for estrone oleate inhibition of the ob gene. This also suggests that leptin may control ob gene expression in white adipose tissue and that estrone oleate may activate this process. The slimming effect of estrone oleate is, thus, not directly dependent on leptin, since both normoleptinemic and hyperleptinemic animals lose fat following treatment nor are the effects on appetite and energy expenditure mediated by leptin. However, leptin levels and the expression of the ob gene are directly linked with estrone oleate function. A possible involvement of leptin in estrone oleate action is postulated. The results support the participation of estrone oleate in the control of body weight and hint at the complexity of its regulation by leptin and glucocorticoids.     

Effect of tamoxifen and tamoxifen derivatives on the conversion of estrone-sulfate to estradiol in the R-27 cells, a tamoxifen-resistant line derived from MCF-7 human breast cancer cells

R-27 cells, a tamoxifen-resistant clone of MCF-7 mammary cancer cells, were used to study the effect of tamoxifen and its derivatives (4-hydroxytamoxifen, N-desmethyltamoxifen and cis-tamoxifen) on the conversion of estrone sulfate to estradiol. The present data indicate that (1) tamoxifen, 4-hydroxytamoxifen, N-desmethyltamoxifen and cis-tamoxifen inhibit the uptake of the radioactivity after incubation of these triphenylethylene derivatives with [3H]-estrone sulfate; (2) there is a significant decrease of the conversion of estrone sulfate to estradiol by these antiestrogens; (3) the concentrations of estradiol (cytosol + 0.6 M KCl nuclear extract) which are 293 +/- 50 pg/mg DNA in the control studies (estrone sulfate alone), diminish to 26 +/- 5 pg/mg DNA after addition of tamoxifen, to 9 +/- 2 with 4-hydroxytamoxifen, to 24 +/- 7 with N-desmethyltamoxifen and to 32 +/- 6 with cis-tamoxifen. It is concluded that estrone sulfate can play an important role in the biological responses to estrogens in this breast cancer cell line and tamoxifen and its derivatives block the conversion of estrone sulfate to estradiol. The decrease in concentration of estradiol could be explained by the presence of the estrogen receptor system but other ways of the action of antiestrogens remain to be explored.     

Luteinizing hormone concentrations in anestrous ewes administered various estrogens

Twenty four anestrous ewes were evenly assigned to one of six groups and administered either sesame oil, estradiol-17β, estradiol-17α, estrone, estradiol benzoate or estradiol valerate. All estrogen treated ewes received 50 μg of the respective estrogen. Blood plasma was collected for 28 hours post-treatment and quantified for luteinizing hormone (LH) by radioimmunoassay. An estrogen induced LH surge was detected in at least three of the four ewes administered either estradiol-17β, estrone, estradiol benzoate or estradiol valerate whereas only one of the four estradiol-17α treated ewes and none of the ewes administered sesame oil had an LH surge. The interval from treatment to peak LH was similar for estradiol-17β (17.3±2.7 hours), estrone (18.5±1.0 hours) and estradiol benzoate (19.0±0.6 hours) treated ewes but delayed 7 to 9 hours for ewes administered estradiol valerate (26.0±1.2 hours).     

Intestinal handling of an oral oleoyl-estrone gavage by the rat

Adult Zucker lean (Fa/?) female rats received a single 250 nmol oral gavage of 3H-labelled oleoylestrone in 0.2 ml of sunflower oil. After one hour, samples of arterial, portal and suprahepatic blood, and lymph were obtained and fractioned to determine the amount of radioactivity present in the form of free estrone, acyl-estrone and hydrophilic estrone esters in the blood of each vessel. Lipoprotein fractions (chylomicra + VLDL, LDL, HDL and lipoprotein-depleted plasma) were also analysed as well as the distribution of absorbed 3H-estrone in the intestine, specific organs and carcass. About one third of the oleoyl-estrone dose recovered was found in the tissues, mainly in the blood, the rest remaining relatively untouched in the intestinal content. High hypothalamic estrone uptake (compared with the rest of the brain) was observed. Data from non-radioactive estrone measurements showed a similar pattern of absorption and tissue distribution to that obtained by 3H-estrone tracking alone. In both cases, most of the estrone present in the intestinal lumen was absorbed as intact oleoyl-estrone, but a significant part was absorbed as free estrone. There is a net transfer of 3H-estrone into portal blood HDL, and part of the 3H-estrone is also loaded into lymph-carried chylomicra. A large share of free estrone is filtered by the liver, but most of the acyl-estrone absorbed passes unaltered. The oral administration of oleoyl-estrone results in significant absorption of the unaltered molecule, which is transferred to lymph-carried chylomicra and also directly to plasma HDLs. It may be inferred that the HDL fraction contains the physiological carrier of oleoyl-estrone in its role of ponderostat signal.