Toxicological assessment of Xanthigen® nutraceutical extract combination: Mutagenicity, genotoxicity and oral toxicity.

Xanthigen® is a nutraceutical combination for weight management capable of increasing energy expenditure via uncoupling protein 1 (UCP-1) in white adipose tissue. It consists of brown seaweed Undaria pinnatifida extract, rich in the carotenoid fucoxanthin (FX) and pomegranate seed oil (PSO), rich in punicic acid. Xanthigen was screened to determine its genotoxicity and 90-days repeated oral toxicity. Genotoxicity was assessed with the Ames test (TA89, TA100, TA1535, TA1537, WP2), chromosomal aberration assay (Chinese hamster ovary cells) and mammalian micronucleus test (in mice). Xanthigen did not exhibit genotoxicity in any tested strain. Sub-chronic toxicity was evaluated with daily oral administration of 250, 500 and 1000 mg/kg/day doses of Xanthigen® to Sprague-Dawley rats over 90 days. No deaths and no deleterious effects were observed during the 90-day treatment, indicating an absence of sub-chronic toxicity and a no observed adverse effect level greater than 1000 mg/kg/day. A statistically significant decrease in bodyweight and food intake in Xanthigen® treated groups was attributed to the weight loss property of Xanthigen®. Overall, Xanthigen® shows no significant mutagenic or toxic effects.

Association of Taq 1B CETP polymorphism with insulin and HOMA levels in the population of the Canary Islands.

BACKGROUND AND AIMS: Cholesteryl ester transfer protein (CETP) is an enzyme with a key role in lipoprotein metabolism. A common genetic polymorphism, the Taq 1B, influences CETP activity and HDL-cholesterol levels, with individual homozygotes for the B1 allele exhibiting higher enzyme activity and lower HDL-cholesterol levels than carriers of at least one B2 allele. Our aim was to analyze the influence of Taq 1B CETP polymorphism on cardiovascular risk factors in a representative sample of adult subjects from Canary population. METHODS AND RESULT: A total of 518 adult subjects from the Canary Islands, enrolled in a nutritional survey (the ENCA study), were included. The Taq 1B polymorphism was analyzed by PCR-RFLP. Compared with individuals with at least one B2 allele, and after adjusting for age, sex, BMI, waist perimeter, smoking and alcohol intake, carriers of the B1B1 genotype showed lower HDL-cholesterol levels (geometric mean (95% CI): 46.6 (44.5-48.8) vs. 50.6 (49.1-52.9)mg/dl; P=0.003); and higher insulin (geometric mean (95% CI): 11.1 (10.5-11.9) vs. 10.0 (9.5-10.5µU/ml; P=0.008) and HOMA levels (geometric mean (95% CI): 2.3 (2.1-2.5) vs. 2.1 (1.9-2.1); P=0.009). In addition, the B1B1 genotype was more frequent in individuals who had low levels of HDL-cholesterol according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria (Odds Ratio (OR): 1.563; 95% CI: 1.04-2.34; P=0.030), and in those included in the upper quartile of insulinemia (OR: 1.90; 95% CI: 1.20-3.03; P=0.007) and HOMA (OR: 1.61; 95% CI: 1.02-2.57; P=0.043). CONCLUSION: The observed influence of Taq 1B polymorphism on insulin levels and HOMA highlights the possible role of CETP in the regulation of glucose homeostasis.

Prevalence of the metabolic syndrome in the island of Gran Canaria: comparison of three major diagnostic proposals.

AIMS: The present study was conducted to estimate the prevalence of the metabolic syndrome in a Canarian population, and to compare its frequency as defined by the most commonly used working definitions. METHODS: Cross-sectional population-based study. One thousand and thirty adult subjects were randomly selected from the local census of Telde, a city located on the island of Gran Canaria. Participants completed a survey questionnaire and underwent physical examination, fasting blood analyses, and a 75-g standardized oral glucose tolerance test. The prevalence of the metabolic syndrome was estimated according to the definitions proposed by the World Health Organization (WHO), the European Group for the Study of Insulin Resistance (EGIR) and the National Cholesterol Education Program (NCEP), the latter with the original (6.1 mmol/l) and the revised criterion (5.6 mmol/l) for abnormal fasting glucose. RESULTS: The adjusted prevalence of the metabolic syndrome was 28.0, 15.9, 23.0 and 28.2%, using the WHO, EGIR, NCEP and revised NCEP criteria, respectively. The measure of agreement (kappa statistic) was 0.57 between the WHO and the original NCEP definitions, and 0.61 between the WHO and the revised NCEP definitions. After excluding diabetic subjects, the agreement between the EGIR and WHO proposals was fairly good (kappa=0.70), whereas concordance of the EGIR with the original and the revised NCEP definitions was moderate (kappa=0.47 and 0.46, respectively). CONCLUSIONS: Whichever the considered diagnostic criteria, the prevalence of the metabolic syndrome in this area of the Canary Islands is greater than that observed in most other European populations.

Intracerebroventricular injections of prolactin counteract the antagonistic effect of bromocriptine on rabbit maternal behaviour.

To investigate the participation of prolactin in nest-building and maternal behaviour in rabbits, we administered (from pregnancy day 26 to parturition) rabbit prolactin (rbPRL; or vehicle) intracerebroventricularly (i.c.v.) to primiparous animals injected with bromocriptine subcutaneously (s.c.). Control females (given vehicle s.c. and i.c.v.) built a maternal nest (of straw and body hair) in 77% of cases. This proportion decreased to 19% in the bromocriptine-only group (P < 0.05) and increased to 93% in the group given bromocriptine plus rbPRL (P > 0.05). Maternal behaviour (i.e. the adoption of a crouching posture over the litter inside the nest box) was expressed by 77% of control rabbits, 19% of bromocriptine-only animals (P < 0.05) and 57% of females given bromocriptine plus rbPRL (P > 0.05). Values of nonmaternal activities (i.e. scent-marking, ambulation in an open field) were similar among the three studied groups. These results suggest that prolactin, acting in late pregnancy, plays a major role in the stimulation of nest-building and maternal behaviour in rabbits.

Effects of tamoxifen on lipid profile and coagulation parameters in male patients with pubertal gynecomastia.

BACKGROUND/AIM: The estrogenic actions of tamoxifen on lipid profiles and hemostasis have been extensively demonstrated in women. Due to limited experience with this drug in males, it is uncertain whether these effects are also present in men. The aim of our study was to assess the response of blood lipids, lipoproteins, and coagulation parameters in a group of men taking tamoxifen. METHODS: We studied 15 healthy boys with pubertal gynecomastia who were given 10 mg tamoxifen per day. Total testosterone, sex-hormone-binding globulin, estradiol, serum lipids, apolipoprotein B, apolipoprotein A-I, lipoprotein(a), fibrinogen, antithrombin III, von Willebrand factor, and markers of activated coagulation and fibrinolysis were determined at baseline and 1 and 3 months after beginning of the tamoxifen treatment. RESULTS: Total cholesterol and lipoprotein(a) showed moderate but significant decreases from baseline. Low-density lipoprotein and high-density lipoprotein cholesterol concentrations as well as triglyceride and apolipoprotein B levels became lower, but these changes were not statistically significant. Among clotting parameters, antithrombin III was reduced, and von Willebrand factor increased significantly. Markers of activated coagulation and fibrinolysis remained unchanged throughout the period of therapy. CONCLUSIONS: The effects of tamoxifen on blood lipids and hemostasis we found in this group of healthy young men were qualitatively similar, but lesser than those previously described in women.

Análisis de la relación (correlación y asociación) entre la p185 y las variables moleculares RE, RP, pS2 y Cat D, en una serie de pacientes con cáncer de mama y ganglias positivos / Analisis of the relationship (correlation and association) between p 185 and the molecular variables RE, RP, pS2, and Cat D in a series of breast cancer patients with positive lymph nodes

Propósito: Analizar los resultados obtenidos de los estudios comparativos entre la sobreexpresión de la oncoproteína p185 determinada cuantitativamente y las variables moleculares RE, RP, pS2 y Cat D. Material y métodos: En una serie de 217 pacientes con cáncer de mama y ganglios positivos, con la oncoproteína p185 determinada cuantitativamente mediante un método ELISA, se llevaron a cabo estudios comparativos de Relación (Correlación y Asociación) del contenido de la p185 con las variables moleculares RE, RP, pS2 y Catepsina D.Resultados: Con una mediana de seguimiento de 50 meses (rango 9-90 meses) en nuestra serie, el estudio de correlación de Pearson entre los transformados logarítmicos de los niveles de p185 y de los receptores estrogénicos y de los receptores de progesterona no mostró correlación alguna, mientras que sí la hubo para la pS2 y la Catepsina D. Resultados similares se obtuvieron en el estudio de correlación de Spearman. Cuando la serie tumoral fue dicotomizada, en el grupo de tumores p185-negativos se observó una correlación positiva para RE, RP, pS2y CD. En el grupo de tumores p185-positivos se encontró una correlación negativa para RE y RP y correlación positiva para la pS2 y CD. La influencia del estado de la p185 sobre el contenido de RE, RP, hS2,CD fue determinada mediante el análisis de Mann-Whitney mostrando que los tumores con la p185 sobreexpresada tenían una mediana de los niveles de RE y RIP muy baja, igual para la pS2 y más alta para la CD que los tumores con concentraciones de p185 inferiores a 260 fmol/mg (35 fmol/mg). Similares resultados se observaron cuando se llevó a cabo el análisis de tabla de contingencia, y cuando los tumores fueron estratificados en cuatro categorías de p185: muy baja (p185 600 fmol/mg).Conclusiones: Nuestros resultados sugieren la identificación de una subpoblación tumoral con un fenotipo más agresivo y, presumiblemente, con un peor comportamiento evolutivo (AU)

Low levels of cathepsin D are associated with a poor prognosis in endometrial cancer.

Total cytosolic cathepsin D (Cat D) levels were estimated by an immunoradiometric assay in a series of 156 consecutive patients with surgical stages I-III primary endometrial adenocarcinoma. Simultaneously, the tissue content of both oestrogen (ER) and progesterone (PR) receptors, and p185HER-2/neu, DNA content (ploidy), and the fraction of S-phase cells (S-phase) were also estimated. Tumoral Cat D content ranged from 0 to 243 pmol mg(-1) protein (median 44 pmol mg(-1) protein) and was not associated with any of the established clinicopathological and biological prognostic variables, with the exception of a weak positive correlation with the tumoral p185HER-2/neu levels. Univariable analysis performed on a subset of 97 patients, followed for a minimum of 2 years or until death, showed that patient age at diagnosis, high histological grade, advanced surgical stage, vascular invasion, positive peritoneal cytology, low levels of Cat D, negative ER and PR status, aneuploidy, and high S-phase were predictive of the presence of persistent or recurrent disease. However, multivariable analysis revealed that only histological grade, surgical stage, Cat D and PR were significantly associated with the patient's outcome. From these findings, we conclude that Cat D is an independent prognostic factor in endometrial adenocarcinoma, its low levels being associated with a worse clinical outcome.

The two native estrogen receptor forms of 8S and 4S present in cytosol from human uterine tissues display opposite reactivities with the antiestrogen tamoxifen aziridine and the estrogen responsive element.

We have investigated the capability of the different native ER forms, present in cytosols from human uterine tissues, of reacting with the antiestrogen [3H]Tamoxifen aziridine ([3H]TA) and with the Estrogen Responsive Element (ERE). Cytosols from uterine leiomyoma (myoma) prepared in buffer containing 40 mM molybdate and protease inhibitors, labelled with [3H]estradiol and analyzed in low-salt sucrose gradient showed 8S and 4S ER forms. The same cytosols labelled with [3H]TA only showed a 4S ER form, whereas the ERE only reacted with fractions from the 8S peak. The band of ERE reaction in the EMSA assay showed a lower relative mobility than the band labelled with [3H]TA, but both bands contained immunoreactive ER of 65 kDa. Electrophoretic mobility of the [3H]TA-labelled band in that system was not affected by cytosol treatment with cross-linkers or SDS, which suggests that it is a monomeric protein. The [3H]TA-binding 4S ER form was found in all studied myoma samples, as well as in human endometrium or myometrium, but not in rat tissues. These results suggest that the 8S and 4S ER form were already present before cytosol from human uterine tissues comes into contact with the molybdate buffer. They both contain the same ER molecule of 65 kDa, either in the free form or as an oligomer. Only the ER dimers, which have been described both in the cytosolic 8S form and in the nuclear 4-5S form, react with the ERE. [3H]TA only binds to the 4S ER monomer probably because its binding site is concealed in the 8S form under these experimental conditions. The opposite reactivity of the 8S and 4S ER forms with [3H]TA and the ERE support the hypothesis that they may constitute separate entities with a different physiological role.

Importance of mother/young contact at parturition and across lactation for the expression of maternal behavior in rabbits.

We prevented mother/pup contact at parturition or across early or midlactation to investigate the importance of such interaction for maintaining material behavior in rabbits. When pup contact was prevented across lactation Days 1-7 or 11-17 (by anesthetizing multiparous mothers during the oxytocin-induced milk letdown; Experiment 1), nursing incidence was reduced to 40% and 83%, respectively, on the day following anesthesia withdrawal. Both groups also showed a decreased milk output, long latencies to initiate nursing, and several entrances into the nest box not associated with nursing. In Experiment 2 we prevented mother/litter contact at parturition to determine the specific role of pup contact at this time. We found a reduction in the incidence of nursing on postpartum Day 1 from 80% (in control primiparous mothers) to 33%. By contrast, 100% of both deprived and control multiparous mothers displayed nursing on Day 1. These mothers also showed the unusual behaviors found in Experiment 1 and an extemporaneous nest-building. We conclude that: (a) mother/young contact at parturition is crucial for establishing maternal responsiveness in primiparous does, (b) the experience acquired by raising a previous litter allows the retention of maternal responsiveness despite a lack of pup contact at parturition, (c) maternal responsiveness is maintained across early lactation by daily interaction with pups, and (d) interaction with pups across midlactation allows the finely tuned display of maternal behavior.

Quantitative analysis of p185(HER-2/neu) protein in breast cancer and its association with other prognostic factors.

The total cellular p185(HER-2/neu) protein (p185) content was measured by ELISA in 346 invasive primary breast cancers, and the results were compared with those of estrogen (ER) and progesterone (PR) receptors, pS2 and Cathepsin D (Cat D) content. At a cut-off level of 260 fmol/mg protein, 53 of the 346 tumors (15%) were p185-positive. A significant positive correlation was observed between p185 levels and those of Cat D, and a weaker, though significant, positive correlation with ER, and pS2 levels, but not with those of PR. However, when only the 293 p185-negative tumors were considered, the correlation between p185 and ER improved substantially, and statistical significance was reached for PR. p185-positive tumors exhibited lower ER and PR content and higher Cat D content than p185-negative tumors. The pS2 content, in contrast, did not undergo significant variation. Tumors considered to be p185-positive were significantly more frequently positive for Cat D at the cut-off of 45 pmol/mg protein, and were more frequently negative for ER and/or PR, but only significant at the cut-off of 15 fmol/mg or higher for both steroid receptors. Finally, p185 status was not associated with menopausal status, tumor size, axillary-lymph-node invasiveness or distant metastases. These results suggest that 260 fmol/mg protein as the cut-off for p185 allows the identification of a tumoral sub-population with a more aggresive phenotype.

Estrogen antagonism on T3 and growth hormone control of the liver microsomal low-affinity glucocorticoid binding site (LAGS).

Male rat liver microsomes contain a low-affinity glucocorticoid binding site (LAGS) capable of binding all natural glucocorticoids and progesterone with a Kd from 20 to 100 nM. The LAGS level is under endocrine control by T3, glucocorticoids and GH. These hormones act synergistically at physiological concentrations to increase the LAGS level. Since female rats show a LAGS level that is much lower than the males (0.15 vs 23 pmol/mg protein, respectively), here we investigated whether estradiol could decrease the LAGS in the male rat. Orchiectomized (OX) male rats showed a higher LAGS level than intact rats. This effect was reversed by implanting a Sylastic capsule containing testosterone. When the OX rats were implanted for 20 days with estrogen capsules that provided an estradiol level in serum of 40 pg/ml, their LAGS level decreased from 23 to 0.2 pmol/mg protein. This effect was not observed in intact male rats and can be partially reversed by testosterone implants into OX rats. Both hypophysectomized male rats and hypothyroid-orchiectomized male rats showed very low levels of LAGS. Administration of physiological doses of GH and/or T3 to these rats greatly increased their LAGS level (from 0.3 to 15 and 16 pmol/mg protein, respectively). Implantation of estrogen capsules to these rats two weeks prior to starting treatment completely inhibited the increase in the LAGS level in response to T3, and significantly decreased the response to hGH, and to a combination of hGH and T3. These results suggest that physiological estradiol levels can antagonize the LAGS induction by T3 and hGH in the male rat, and could be responsible for the low level of LAGS in the female rat. Moreover, estrogen capsules also inhibited the increase in the body and hepatic weights observed after hGH treatment, which suggests a powerful inhibitory effect of low estradiol levels on the male rat liver functions under regulation by T3 and/or GH.

Identification of a specific binding site for the anabolic steroid stanozolol in male rat liver microsomes.

Male rat liver microsomes contain a [3H]dexamethasone binding site, capable of binding glucocorticoids and progesterone. We have shown previously that the 17 alpha-alkylated androgen, stanozolol, can inhibit the [3H]dexamethasone binding to microsomes through a negative allosteric mechanism, which gives rise to the possibility of its interaction with a different binding site. In this study, the existence of a single-saturating binding site, capable of binding the radioactive steroid with a maximum number of the specific binding site of 49 +/- 2 pmol/mg of protein and a Kd of 37 +/- 1.3 nM was demonstrated by using [3H]stanozolol. In competition experiments, only stanozolol and danazol were able to compete with [3H]stanozolol for its binding to microsomes, among more than 60 steroids and other compounds tested. The binding of [3H]stanozolol was depressed after protease treatment of the microsomes, or after the administration of cycloheximide to adult male rats for 24 hr, which suggest its proteic nature. The [3H]stanozolol binding site was detected in many tissues of the rat, with the highest concentrations being found in the liver. It was detected from birth, increasing afterward in concentration and reaching a peak at 2 to 3 months of age. This is the first experimental verification of the existence in liver microsomes of a specific binding site for some 17 alpha-alkylate androgens, such as stanozolol and danazol, different from the androgen receptor or the [3H]dexamethasone binding site.

Validation of a differential PCR and an ELISA procedure in studying HER-2/neu status in breast cancer.

HER-2/neu oncogene status and total cellular p185HER-2 content were simultaneously analyzed in 415 invasive breast-cancer specimens by differential PCR and ELISA respectively. Mathematical analysis of the data led us to establish a cut-off value of 1.7 for the ratio between the intensity of the HER-2/neu gene band and the reference gene band, to consider the HER-2/neu gene amplified, and of 260 fmol/mg protein, to consider p185HER-2 over-expressed. Of the 415 tumors studied, 15% showed a diverse degree of HER-2/neu gene amplification. Of these tumors, 87% showed over-expression of the p185HER-2. Of the remaining 352 specimens that did not display HER-2/neu gene amplification, 97% showed no p185HER-2 over-expression (p < 0.0001). In 40 selected samples with a p185HER-2 level lower than 260 fmol/mg protein, the degree of p185HER-2 phosphorylation was very low or undetectable. Conversely, 38 of 46 selected tumors with a p185HER-2 level higher than 260 fmol/mg protein exhibited a considerable degree of p185HER-2 phosphorylation (p < 0.0001). Our data suggest that: (i) differential PCR and ELISA, which are relatively simple procedures, give similar information on HER-2/neu status in breast cancer; and (ii) given the large series analyzed, the cutoff values established can be considered as safe values for determining whether, in a given tumor, the HER-2/neu oncogene is amplified or p185HER-2 is over-expressed.

Effects of tamoxifen on serum lipid and apolipoprotein levels in postmenopausal patients with breast cancer.

Serum lipids and apolipoprotein levels were measured in twenty postmenopausal women with primary breast cancer, before and three months after tamoxifen therapy (10 mg twice a day). Tamoxifen caused a significant reduction in total serum cholesterol (10%; P < 0.02), and in low-density lipoprotein cholesterol (17%; P < 0.01), and a significant 47% increase in the subclass 2 of the high density lipoprotein cholesterol (P < 0.01). In addition, tamoxifen caused a 16% increase in apolipoprotein A-I, a 12% decrease in apolipoprotein B (P < 0.05), and a 37% reduction in the serum concentration of lipoprotein (a) (P < 0.01). These results show that tamoxifen brings about an important improvement in serum lipid profile.

[3H]dexamethasone binding activity in liver microsomes is modulated differently by 17 alpha-alkylated androgens and testosterone in vivo.

Rat liver microsomes contain a single class of steroid binding sites, capable of binding various glucocorticoids and progesterone. In a previous article, we have described the in vitro interaction of several androgens with this binding site. Unlike natural androgens, the 17 alpha-alkyl derivatives stanozolol and danazol were capable of interacting with this binding site through a negative allosteric pattern. Now, the effects these steroids exert on the microsomal [3H]dexamethasone binding site have been studied in vivo. The administration of a single dose of stanozolol to rats provoked a significant reduction in the microsomal [3H]dexamethasone binding capacity. This effect was maximal two hr after stanozolol administration and persisted for six hr. The restoration of the [3H]dexamethasone binding level after stanozolol administration was dependent on protein synthesis, since it was blocked by the concomitant administration of cycloheximide. None of the other androgens tested (danazol, methyltestosterone, fluoxymesterone, and testosterone propionate) was capable of provoking a similar effect when administered 2 or 24 hr prior to sacrifice. In rats treated for seven days with a daily dose of diverse androgens and sacrificed 24 hr after the last treatment, none of the 17 alpha-alkyl androgens assayed provoked significant changes in the microsomal [3H]dexamethasone binding level, although stanozolol, danazol, and methyltestosterone provoked a significant increase in glucocorticoid receptor concentration. In contrast, the administration of testosterone propionate provoked a 50% reduction in the [3H]dexamethasone binding level without causing changes in the glucocorticoid receptor concentration. These results provide new evidence on the existence of different effects on the liver of 17 alpha-alkyl androgens, compared to the effects produced by natural androgens.

Ethinylestradiol interacts with liver microsomes and induces binding sites for steroid hormones in the male rat liver.

The present work focuses on the interaction of 17 alpha-ethinyl estrogen derivatives with the [3H]dexamethasone ([3H]DEX) binding site from male rat liver microsomes and the induction of this site by the in vivo administration of natural and synthetic estrogens. [3H]DEX binds to a single-saturating binding site (Kd = 100 nM; maximal binding = 13 pmol/mg of protein) in the liver microsomes. In competition experiments, ethinylestradiol (EE2) and mestranol were able to inhibit [3H]DEX binding to microsomes, whereas natural estrogens, tamoxifen or estrogen sulfates were ineffective. Saturation analysis performed by incubating [3H]EE2 with liver microsomes revealed the existence of a low-affinity (Kd = 280 +/- 30 nM) and high capacity (maximal binding = 16 +/- 2 pmol/mg of protein) binding site. Saturation, competition and dissociation experiments suggest that [3H]DEX and [3H]EE2 interact with the same microsomal entity. Synthetic and natural estrogens increased the hepatic expression of the [3H]DEX binding site in immature, hypothyroid and hypophysectomized male rats. This induction required at least 2 days of treatment, and could only be achieved by pharmacological doses of estrogens.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related changes in the induction of tyrosine aminotransferase by dexamethasone: correlation with the low-affinity glucocorticoid binding sites.

Rat liver membranes contain Low-affinity glucocorticoid binding sites (LAGS), capable of binding with low affinity (Kd approximately 100 nM) endogenous glucocorticoids. Unlike the glucocorticoid receptor (GR), the LAGS level undergoes abrupt changes throughout life. The investigation of these changes may be useful in determining whether the LAGS are involved in the cellular response to glucocorticoids. For this purpose, we have studied glucocorticoid induction of tyrosine aminotransferase (TAT), and its relationship with the LAGS level in adrenalectomized and fasted rats of different ages. No significant differences in the GR level, or in its Kd and activation, were observed among rats of 1, 3, and 12 months of age. On the other hand, the LAGS level showed an important variation with age, from almost undetectable in 1-month-old rats, to a maximum value in 3-month-old rats. With respect to TAT activity, an increase with age in the threshold of response to dexamethasone (DEX) administration was observed. The smallest dose of DEX capable of provoking a significant TAT induction rose from 0.1 microgram/kg body wt. in 1-month-old rats to 10 micrograms/kg body wt. in 12-month-old rats. However, the smallest dose of DEX able to elicit the maximal response was 10 micrograms/kg body wt. in all the assayed ages. This dose provoked a 40% decrease in the GR level, but did not significantly modify the LAGS content. From these results, we conclude that there is an age-related change in the threshold of response to DEX that cannot be explained by the GR-glucocorticoid interaction. The possibility that the LAGS modulate the cell response to glucocorticoids arises from the coincidence of this change with that observed in the LAGS concentration throughout life.

The role of growth hormone in regulation of low affinity glucocorticoid-binding sites from male rat liver microsomes.

GH participates in the regulation of the expression of several hepatic proteins, some of which are subject to multihormonal control. We have previously shown the participation of glucocorticoids and thyroid hormones in the regulation of the hepatic low affinity glucocorticoid-binding sites (LAGS). Here, we provide evidence that also implicates GH in the endocrine control of the LAGS through the use of several animal models, all of them having a very low or undetectable plasma GH level: the hypothyroid (TX), the hypophysectomized, and the GH-deficient Lewis-derived dwarf rat. In dwarf rats, the level of LAGS was only 35% of that found in normal Lewis rats. Treatment of these rats with human (h) GH significantly increased the LAGS level in a dose-response manner. In TX rats, hGH treatment provoked a significant increase in the LAGS level (from 0.9 +/- 0.2 to 7.2 +/- 0.8 pmol/mg protein), so that it represented about 65% of the level found in intact animals. In both hypothyroid-adrenalectomized and hypophysectomized rats, the isolated effect of hGH was not as pronounced as in TX or dwarf rats; however, a potentiation of the effect of hGH was observed when this hormone was injected together with corticosterone acetate. On the other hand, when hGH, T3, and corticosterone acetate were given in combination to hypophysectomized rats, hGH and T3 behaved as agonists of the LAGS induction at T3 doses lower than or equal to 0.1 microgram/100 g BW and as antagonists at T3 doses higher than this. When T4 was used instead of T3, this hormone was capable of potentiating the effect of hGH at doses lower than or equal to 1.5 micrograms/100 g BW. From these results we conclude that 1) GH as well as thyroid and glucocorticoid hormones participate in the endocrine regulation of the LAGS; and 2) under physiological conditions, it is conceivable that GH, thyroid hormones, and glucocorticoids act synergistically in the endocrine regulation of the LAGS.

Stanozolol and danazol, unlike natural androgens, interact with the low affinity glucocorticoid-binding sites from male rat liver microsomes.

Some 17 alpha-alkylated androgens used as anabolic agents, such as stanozolol (ST) and danazol (DA), have specific effects on the liver that are not exerted by testosterone. This gives rise to the possibility that a steroid-binding protein, other than the androgen receptor, could modulate the intracellular actions of these agents. Male rat liver microsomes contain a homogeneous population of [3H]dexamethasone ([3H]DEX)-binding sites which we have denominated low affinity glucocorticoid-binding sites (LAGS). Because glucocorticoids, progestagens, and the synthetic estrogen ethynyl estradiol compete with [3H]DEX for binding to the LAGS, we aimed to study the possible interactions between androgens and the LAGS. To investigate whether several androgens had the capability of interacting with the LAGS, we performed competition experiments. The LAGS had no affinity for testosterone or methyltrienolone (R1881). However, some 17 alpha-alkylated androgens (DA (IC50, 116 nM) > ST >> fluoxymesterone > mestaline > methandriol >> methandrostenolone > methyltestosterone) were able to compete with [3H]DEX binding to liver microsomes. ST and DA were potent inhibitors of [3H]DEX binding to liver microsomes. They decreased both the affinity and the number of [3H]DEX-binding sites, increased the dissociation rate of [3H]DEX from the LAGS, and provoked a time- and dose-dependent inactivation of the [3H]DEX-binding site. These results strongly suggest that ST and DA exert a negative allosteric modulation on [3H]DEX binding to the LAGS. The in vivo administration of ST (but not other androgens) to male rats provoked a time- and dose-dependent decrease in the LAGS level. Full recovery of the LAGS concentration required at least 8 h and was blocked by protein synthesis inhibitors. Such results suggest that ST irreversibly inactivates the [3H]DEX-binding site in vivo as it does in vitro. Taken together, these observations are indicative of an irreversible interaction between some 17 alpha-alkylated androgens and the LAGS both in vitro and in vivo and suggest that ST may be an important pharmacological tool that can be used in the elucidation of the molecular structure of the LAGS. These results also mean that the LAGS are a steroid-binding entity able to distinguish between natural androgens and 17 alpha-alkylated testosterone derivatives used as anabolic agents.

Prolactin stimulates emission of nipple pheromone in ovariectomized New Zealand white rabbits.

Using ovariectomized New Zealand white rabbits and the nipple-search behavior of pups as a bioassay, we evaluated the capacity of prolactin to stimulate the emission of an odor signal that allows newborn pups to locate the mother's nipples and suckle. Whereas emission of this so-called nipple pheromone was minimal in untreated, ovariectomized does, emission was stimulated by the administration of progesterone (1 mg/day) to estrogen-treated does (0.5 microgram estradiol benzoate/day) and decreased after withdrawal of progesterone despite continuous administration of estrogen. However, substituting ovine prolactin (1.5 mg/day) for progesterone, under continuous estrogen administration, resulted in an increase in pheromone emission to near-maximal levels. This stimulatory effect of prolactin was not progesterone-dependent since it also occurred in does pretreated with estrogen alone and, to a lesser extent, even in females without estrogen priming. From these and previous data, we propose that emission of nipple pheromone in the rabbit is induced during pregnancy by the combined action of estrogen and progesterone, and maintained during lactation by the dual action of estrogen and prolactin.