Castrated Female Rats Research Articles

FK506 ameliorates osteoporosis caused by osteoblast apoptosis via suppressing the activated CaN/NFAT pathway during oxidative stress.

Osteoporosis is affecting the health of postmenopausal women in the world. In case of that, we explored whether FK-506 could ameliorate osteoporosis by inhibiting the activated CaN/NFAT pathway during oxidative stress. First, the castrated rat model is constructed through the bilateral ovariectomy. Hologic Discovery (S/N 80347) dual-energy X-ray absorptiometry assessed bone mineral density (BMD) implemented at left femur of rats. Next, hematoxylin-eosin (H&E) staining observed and calculated the changes of bone trabecular, mean trabecular plate separation (Tb.Sp), mean trabecular plate thickness (Tb.Th), and bone volume fraction (BV/TV). Then, CCK-8 assay, TUNEL assay, ALP kit and alizarin red staining detected the viability, apoptosis, alkaline phosphatase (ALP) activity, and capacity of mineralization respectively. At last, commercially available kits detected the levels of ROS and SOD in transfected MC3T3-E1 cells and bone tissues, and Western blot analysis detected proteins related to apoptosis and CaN/NFAT pathway. FK-506 increased the BMD and changes of bone trabecular in female castrated rats. FK-506 inhibited the oxidative stress and apoptosis by suppressing the activated CaN/NFAT pathway. Low dose of FK-506 improved the viability, ALP activity, and mineralization capacity. What's more, it suppressed the apoptosis of H2O2-induced MC3T3-E1 cells, which was deteriorated by the high dose of FK-506. Briefly, low dose of FK-506 inhibited the oxidative stress by suppressing the activated CaN/NFAT pathway, while high dose of that further inhibited the oxidative stress by suppressing the CaN/NFAT pathway. FK-506 ameliorates osteoporosis resulted from osteoblastic apoptosis which caused by suppressing the activated CaN/NFAT pathway during oxidative stress.

Sex differences in the excretion levels of traditional and novel urinary biomarkers of nephrotoxicity in rats.

Urinary biomarkers have been used widely in preclinical toxicity studies to detect dysfunctions and injuries of the kidney caused by drugs under development. While they have been well studied for evaluating nephrotoxicity, knowledge of sex differences in excretion levels of urinary biomarkers remains inadequate. We conducted experiments focused on effects of endogenous sex hormones on urinary biomarkers using intact and castrated male and female rats. Comparisons of the urinary biomarker excretion levels between intact male and female rats at 5, 7, 9 and 12 weeks of age revealed higher excretion levels of leucine aminopeptidase (LAP), γ-glutamyl transpeptidase (γGTP), total protein, liver-type fatty acid-binding protein (L-FABP), cystatin C (Cys-C) and β2-microglobulin (β2-MG), and lower excretion level of kidney injury molecule 1 (Kim-1), in male rats as compared to female rats. Orchidectomized male rats showed lower urinary excretion levels of alkaline phosphatase (ALP), LAP, γGTP, N-acetyl-β-D-glucosaminidase (NAG), glucose, total protein, L-FABP, Cys-C, β2-MG and neutrophil gelatinase-associated lipocalin (NGAL), and higher urinary excretion levels of clusterin (CLU) and Kim-1, than sham-operated male rats. On the other hand, no significant differences in the urinary biomarker excretion levels excluding ALP were observed between ovariectomized and sham-operated female rats. In the present study, we demonstrated the existence of sex differences in excretion levels of urinary biomarkers that are universally used in preclinical toxicity studies, and also that these differences, especially in relation to the urinary excretions of ALP, LAP, γGTP, total protein, L-FABP, Cys-C, and β2-MG, may closely relate to the endogenous testosterone.

Ameliorative effect of androgen therapy tear on film stability in castrate female rats

Background Prevalence of dry eye is significantly inceasing in postmenopausal women than that in men, suggesting that sex hormone plays a role in the pathogenesis of dry eye. In addition, dry eye might become worse following estrogen therapy in postmenopausal women. However, whether application of androgen can ameliorate dry eye is being concerned. Objective This study was to investigate the effect of androgen on tear film of ovariectomized female rats. Methods Forty-eight 3-month-old sexually mature female Wistar rats were randomized into the normal control group, sham group, ovariectomy (OVX) model group and testosterone-injected group. OVX models were established by bilateral ovaries enucleation in the rats of the model group and testosterone-injected group, and then androgen (3.75 mg/kg) was intramuscularly injected since 5 months after OVX at 3-day interval for 6 weeks. Only intraperitoneal fat was cut off in the sham group. In 6 weeks after injection of androgen, serum androgen concentration detected and Schirmer Ⅰtest (SⅠt), tear film break-up time (BUT) were performed. The rats were sacrificed to prepare the corneal and conjunctival samples. The expression of MUC5AC in conjunctival tissue was examined by immunofluorescence staining, and the microstructure of corneal cellular surface was observed under the scanning electron microscope before and 6 weeks after application of androgen. Animals in this study were treated in accordance with Animal Experimentation Ethic Committee Guidelines of Southern Medical University and the study protocol was approved by Ethic Committee of this University. Results The mean serum testosterone concentration was (1.83±0.12)ng/ml, and SⅠt or BUT was (3.63±0.26)mm/5 minutes or (3.73±0.38)seconds, respectively, in the OVX model group, which was significantly declined in comparison with (2.56±0.14)ng/ml, (7.47±0.66)mm/5 minutes or (9.57±0.76)seconds in the normal control group (all at P=0.000). However, the serum testosterone concentration was (3.38±0.24)ng/ml, SⅠt was (6.37±0.45)mm/5 minutes and BUT was (7.54±0.55)seconds in the testosterone-injected group, which was significantly higher than that in the OVX model group (all at P=0.000). The positive staining of MUC5AC in rat conjunctival tissue weakened in the OVX model group compared with the normal control group, and the fluorescence intensity in the testosterone-injected group was stronger than that in the OVX model group. Regularly arranged microvilli and cell metabolism hiatus on the surface of corneal cells were seen in the normal control group and the sham group; while the microvilli were shorter and irregularly arranged, and the cell metabolism hiatus were disappeared in the OVX model group. However, microvilli and cell metabolism hiatus were close to normal ones in the testosterone-injected group. Conclusions Deterioration of tear secretion and instability of tear film are are probably associated with the lower serum androgen levels in castrated female rats. Systemic supplement of androgen can promote tear secretion, improve tear film stability and alleviate ocular surface damage. Key words: Dry eye/therapy; Tears/secretion; Ovariectomy; Androgens/drug therapy; Disease models, animal; Rats, Wistar; Female

Gender different response to immunonutrition in liver cirrhosis with sepsis in rats.

Females with sepsis have a better prognosis than males, while those of both genders with cirrhosis have a high mortality. Impaired immunity accompanies liver cirrhosis. The potential association between sex and immunologic response of cirrhotic rats in sepsis following immunonutrition was investigated. One hundred and forty-three rats were randomly divided into groups. Liver cirrhosis was produced by weekly feeding of CCl4 for 8 weeks. Among them, 24 male and 19 female underwent castration one month before studying. The rats were fed with either immune enhancing diet or control diet for five days, then sepsis was induced with cecal ligation and two holes puncture. Main outcomes included mortality and serum cytokines (IL-1β, 6, and 10). Comparisons were made both within and between genders. Cirrhotic non-castrated male rats showed a significant decrease in mortality (64.1% vs. 32.1%, p = 0.032) with better survival than control diet following immune enhancing diet. Lower mortality of cirrhotic non-castrated female rats was found after immune enhancing diet (69.6% vs. 52.1%, p = 0.365). Cirrhotic castrated male rats showed a lower mortality (44.4%) following immune enhancing diet, and cirrhotic castrated female rats also showed significantly lower mortality and better survival than control diet after immune enhancing diet (87.5% vs. 33.3%, p = 0.004). Plasma concentrations of IL-1β were higher in non-oophorectomized female rats fed with control diet compared to immune enhancing diet. Non-orchidectomized males and non-oophorectomized females exhibited similar increases in IL-10 after immune enhancing diet. Our results demonstrated that immunonutrition was more beneficial for male than female cirrhotic rats following sepsis. Though orchidectomy was not found to be more advantageous for the normal male rats in sepsis, immunonutrition seemed to be as important as sex hormone for female rats in sepsis.

Disappearance of gender‐related difference in the toxicity of benzotriazole ultraviolet absorber in juvenile rats

2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole (HDBB) is an ultraviolet absorber used in plastic resin products, such as building materials and automobile components. In oral repeated dose toxicity studies using 5- or 6-week-old rats, this chemical induced hepatic histopathological changes, such as hypertrophy accompanied with eosinophilic granular changes and focal necrosis of hepatocytes, and male rats showed nearly 25 times higher susceptibility to the toxic effects than females. Castration at approximately 4 weeks of age markedly reduced the sex-related variation in HDBB toxicity, but some difference, less than five times, remained between male and female castrated rats. Following oral HDBB administration to male and female juvenile rats from postnatal days 4-21, such gender-related difference in toxic susceptibility was not detected; therefore, it is speculated that the determinants of susceptibility to HDBB toxicity are differentiated between sexes after weaning. In young rats given HDBB, there was no gender-related difference in plasma HDBB concentration, and no metabolites were detected in the plasma of either sex. HDBB induced lauric acid 12-hydroxylase activity in the liver and this change was more pronounced in males than in females. These findings indicate that HDBB could show hepatic peroxisome proliferation activity, and the difference in the susceptibility of male and female rats to this effect might lead to marked gender-related differences in toxicity.

Effect of 5α-Reduced Androgens on Prolactin Secretion

The effects of a 6-day treatment with 2 mg/day of testosterone, dihydrotestosterone (DHT), 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol) and 5 alpha-androstan-3 beta, 17 beta-diol (3 beta-diol) on serum prolactin levels have been evaluated in long-term castrated male and female rats. The steroids were administered either in the free alcohol or in the propionated form (mono and dipropionates for the 3 alpha- and 3 beta-diols). Practically no effect of any steroid was evident in the treated male animals. DHT and 3 alpha-diol inhibited prolactin secretion in the female animals, while testosterone and 3 beta-diol remained ineffective. The data suggest a possible role of 5 alpha-reduced compounds, DHT and 3 alpha-diol in the control of prolactin secretion in females.

Effects of Trifolium pratense and Cimicifuga racemosa on the endometrium of wistar rats

ObjectiveThe aim of this study was to evaluate the effects of Trifolium pratense and Cimicifuga racemosa upon the endometrium of castrated female Wistar rats, comparing these results with a placebo and estradiol valerate. MethodsThirty-two adult castrated female Wistar rats were divided into four groups (eight rats per group) that receiving either tap water, estradiol valerate, isoflavones from T. pratense or deoxyactein from C. racemosa daily. The doses used were equivalent to normal doses used in humans. The results were analyzed by endometrial histology and the expression of α-estrogen receptor and protein Ki67. Both α-receptor and Ki67 expressions were determined by immunohistochemical and morphometric analysis. ResultsEndometrium histology stayed atrophic with both herbal extracts, but T. pratense supplementation increased the expression of α-estrogen receptors when compared to the placebo group, without protein Ki67 expression enhancement. Both herbal extracts presented a lower Ki67 expression when compared to the placebo group. ConclusionT. pratense presented α-estrogen receptor stimulation in the endometrium without increasing cell proliferation. Both herbal extracts reduced endometrial proliferation in comparison to the placebo group.

Melatonin is able to prevent the liver of old castrated female rats from oxidative and pro‐inflammatory damage

The aim of this study was to investigate the effect of aging and ovariectomy on various physiological parameters related to inflammation and oxidative stress in livers obtained from old female rats, and the influence of chronic administration of melatonin on these animals. Twenty-four female Wistar rats of 22 months of age were used. Animals were divided into four experimental groups: two intact groups that were untreated or given melatonin (1 mg/kg/day), and two ovariectomized groups that also untreated and treated with melatonin (1 mg/kg/day). After 10 wk of treatment, rats were sacrificed by decapitation, and livers were collected and homogenized. A group of 2-month-old female rats was used as young controls. Protein expression of inducible nitric oxide synthase (iNOS), heme oxygenase-1 (HO-1), IL-6, TNF-alpha and IL-1beta were determined by Western blot analysis. The levels of nitric oxide metabolites (NO(x)), lipid hydroperoxide (LPO), TNF-alpha, IL-1beta, IL-6 and IL-10 were determined. Levels of LPO in the liver homogenates as well as iNOS protein expression and NO(x) levels were increased in old rats as compared with young animals; this effect was more evident in ovariectomized animals. Pro-inflammatory cytokines TNF-alpha, IL-1beta and IL-6 were significantly increased and anti-inflammatory IL-10 decreased during aging and after ovariectomy. Aging also significantly increased the expression of HO-1 protein, and ovariectomized rats showed an additional increase. Administration of melatonin, both to intact and to the ovariectomized animals significantly reduced NO(x), LPO levels and pro-inflammatory cytokines in the liver as compared with untreated rats. Significant rice in IL-10 and reductions in the iNOS, HO-1, IL-6, TNF-alpha and IL-1beta protein expression were also found in rats treated with melatonin. Oxidative stress and inflammation induced during aging in the liver are more marked in castrated than in intact females. Administration of melatonin reduces both these situations.

Effects of raloxifene on the urethra of adult castrated female rats

Objective The objective of this study was to evaluate the effects of raloxifene on the weight and epithelial thickness of the urethra of castrated female rats.Methods Forty castrated female rats were randomly separated into two groups: group I (control, n = 20) received only the vehicle, and group II (raloxifene, n = 20) received 750 μg/day of raloxifene for 30 days. On the 31st day, the animals were sacrificed and the urethras were removed for the study. A model for categorical data using the weighted minimum mean square error method and Student's t test were used for the data analysis (p < 0.05).Results The mean weights of the urethras in groups I and II were 22 ± 1.6 mg and 24 ± 1.7 mg, respectively (p = 0.371). There was an increase in the mean epithelial thickness of the distal segments in group II compared to group I (50.7 ± 1.9 μm vs. 45.3 ± 1.6 μm, respectively) (p < 0.04). No statistically significant difference was found in the mean epithelial thickness of the proximal urethra between the two groups (p = 0.187).Conclusion Raloxifene administered to castrated female rats for 30 days increased the distal urethral epithelial thickness and did not alter the weight of the urethra.

Gender-Related Difference in the Toxicity of Ultraviolet Absorber 2-(3′,5′-Di-tert-butyl-2′-hydroxyphenyl)-5-chlorobenzotriazole in Rats

2-(3′,5′-Di-tert-butyl-2′-hydroxyphenyl)-5-chlorobenzotriazole (DBHCB) is widely used as an ultraviolet absorber. Previously, we showed that male rats had more than a 100 times higher susceptibility to the toxic effects of DBHCB than females. In order to investigate the role of sex steroids in the mediation of this gender-related difference, DBHCB (0 or 250 mg/kg/day) was given to male and female young intact and castrated rats by gavage for 28 days in the current study. In intact rats, relative liver weight increased to more than two times that of the control in males, while the rate of change was less than 10% in females. On histopathology, hypertrophy of hepatocytes was observed in males but not in females. In castrated rats, an approximately 40% increase in the relative liver weight was found only in males, and no histopathological changes in the liver were detected in either sex. The gender-related difference was also determined in preweaning rats administered DBHCB at 0, 250, or 500 mg/kg/day by gavage from postnatal days 4 to 21. Blood biochemical changes, including increases in the levels of AST, ALT, and ALP, 80–95% increase in the relative liver weight and histopathological changes in the liver, such as hypertrophy and single cell necrosis of hepatocytes, were observed at both doses in both sexes. In conclusion, the gender-related difference in the toxicity of DBHCB, which was observed in young rats, was markedly reduced by castration and abolished in preweaning rats.

The effects of soy extract on the uterus of castrated adult rats

Objective The aim of this study was to evaluate the effects of different doses of a standardized soy extract on the uterus of castrated rats. Methods Fifty-six adult castrated female Wistar rats were randomly divided into seven groups (eight animals in each) that received: GI—drug vehicle (propylene glycol); GII—soy extract 10 mg/kg per day; GIII—soy extract 50 mg/kg per day; GIV—soy extract 100 mg/kg per day; GV—soy extract 300 mg/kg per day; GVI—soy extract 600 mg/kg per day; GVII—conjugated equine estrogens (CEE) 200 μg/kg per day. After 21 days of treatment, all animals were sacrificed and fragments of the uterine horns were immediately removed, fixed in 10% formaldehyde and submitted to routine histological techniques for morphometric study. The endometrial cell proliferation index was determined with the PCNA antibody PC-10 and expressed as the percentuals of the PCNA-positive nuclei relative to the total countings. Other fragments were immediately frozen in liquid nitrogen for RNA extraction and VEGF analysis using RT-PCR technique. Results The minimal dose of soy extract that produced a significant increase of the morphometric parameters was 100 mg/kg (GIV). The maximum effects on endometrial and myometrial morphometry were detected in the groups treated with 300 and 600 mg/kg of soy extract (groups V and VI) and CEE (GVII). The expression of PCNA in the endometrial epithelium and stroma was increased by treatment with 100–600 mg/kg per day of soy extract (groups IV–VI) or with CCE (group VII). Doses equal to or higher than 50 mg/kg of soy extract (groups III–VI) and CEE stimulated the expression of VEGF. Conclusion The treatment of adult castrated rats during 21 days with doses of 100 mg/kg per day or higher of soy extract may determine significant proliferation in the endometrium and myometrium.

Effects of Korean Red Ginseng on the Vaginal Blood Flow and Structure in Female Castrated Rats

Purpose: Ginseng is a traditional Asian remedy for sexual dysfunction. The purposes of this study were to investigate the effects of Korean red ginseng (KRG) on the vaginal blood flow and tissue structure in female castrated rats. Materials and Methods: Female Spague-Dawley rats (200-210gm) were divided into 4 groups: the control (n=20), castration (n=30), and castration plus oral administration of KRG extracts (50 and 100mg/kg/day, n=15 and n=15, respectively). After 1 month of treatment, the serum estrogen and total cholesterol levels were measured. The vaginal blood flow was measured using laser Doppler flowmeter before and after pelvic nerve stimulation (PNS). The vaginal tissue was processed for Masson's trichrome stain, immunohistochemistry and Western blotting. Results: The serum estrogen level was significantly decreased in the castration group (0.8±1.9ng/ml); however, it increased up to the control level (2.2±1.3ng/ml) in both the KRG administration groups (p<0.05). The PNS-induced vaginal blood flow tended to improve in the KRG treatment groups. On the histology, the vaginal epithelial layer and submucosal microvasculature showed improvement in the KRG treatment groups. The expression of estrogen receptor increased in the KRG treatment groups compared to the castration group. Conclusions: These results suggested that KRG extracts seem to have an estrogenic effect on castrated female rats. This implies that the KRG extracts may have an ameliorating effect on sexual function in menopausal woman. (Korean J Urol 2006;47:888-894) ꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏ

Phosphodiesterase expression targeted to gonadotropin-releasing hormone neurons inhibits luteinizing hormone pulses in transgenic rats.

Experiments in the GT1 gonadotropin-releasing hormone (GnRH) cell line have shown that the cAMP signaling pathway plays a central role in regulating the excitability of the cells. Lowering cAMP levels by expressing the constitutively active cAMP-specific phosphodiesterase PDE4D1 in GT1 cells inhibited spontaneous Ca2+ oscillations and intrinsic pulsatile GnRH secretion. To address the role of cAMP levels in endogenous GnRH neurons, we genetically targeted expression of PDE4D1 (P) to GnRH neurons in transgenic rats (R) by using the GnRH gene promoterenhancer regions (G). Three lines of transgenic rats, GPR-2, -4, and -5, were established. In situ hybridization and RT-PCR studies demonstrated that transgene expression was specifically targeted to GnRH neurons. Decreased fertility was observed in female but not in male rats from all three lines. The mean luteinizing hormone (LH) levels in ovariectomized rats were significantly reduced in the GPR-4 and -5 lines but not in the GPR-2 line. In castrated male and female GPR-4 rats, the LH pulse frequency was dramatically reduced. Six of twelve GPR-4 females studied did not ovulate and had polycystic ovaries. The remaining six females ovulated, but the magnitude of the preovulatory LH surge was inhibited by 63%. These findings support the hypothesis that cAMP signaling may play a central role in regulating excitability of GnRH neurons in vivo. The GPR-4 line of transgenic rats provides a genetic model for the understanding of the role of pulsatile gonadotropin release in follicular development.

Development of an experimental ovarian tumor: immunocytochemical analysis.

The aim of the present work was to study whether immunocytochemical parameters present in the normal ovary were altered after tumor development under high gonadotropin levels. Ovarian tumors (luteoma): castrated female rats had an ovary grafted into the spleen; tumors were left to develop for 1, 2, 3 or 7 months. The presence of apoptotic cells (TUNEL method) and the expression of proliferating cell nuclear antigen (PCNA), gap junction protein (Cx43), steroidogenic acute regulatory protein (StAR), aromatase and synaptosome-associated protein of 25 kDa (SNAP-25) were determined by immunocytochemistry. Some of these findings were confirmed by RT-PCR (Cx43, StAR, SNAP-25). Inhibin subunit mRNAs were investigated by Northern blot. PCNA staining of tumors was mainly found in granulosa cells of transforming follicles and was absent from luteinized follicles. A nearly complete absence of apoptosis was observed. Cx43 was mainly found in follicles, while it was very weakly expressed or absent in luteinized follicles. StAR protein expression, indicating active steroidogenesis, was demonstrated only in luteinized follicles and in thecal cells, but was absent from granulosa cells. Aromatase immunoreactivity was very intense in granulosa and also present in luteal cells. Membrane-associated and cytoplasmic SNAP-25 immunostaining was determined in patches of endocrine cells in the follicles, as well as in the luteinized follicles. The expression of mRNAs for Cx43, StAR and SNAP-25 (RT-PCR) and inhibin subunits (Northern blots) were confirmed in 1-, 3- and 7-month-old tumors. These results indicated that luteoma most likely develop from unruptured follicles by hypertrophy and proliferation of follicular cells. Circulating gonadotropins seem to play a fundamental role in maintaining the expression of proteins typically expressed in normal ovary, while avoiding apoptosis in this tissue.

Improvement of a two-stage carcinogenesis model to detect modifying effects of endocrine disrupting chemicals on thyroid carcinogenesis in rats

In order to improve the sensitivity of our previously established thyroid carcinogenesis model and to clarify whether endocrine disrupting chemicals with weak estrogenic activity have any modifying effects on the development of thyroid proliferative lesions, 6-week-old female castrated F344 rats were first given a single subcutaneous injection of 2000 mg/kg body weight of N-bis(2-hydroxypropyl)nitrosamine. From 1 week later, they received diets with: no supplement (basal diet (BD) group); cholesterol pellets containing 0.5 mg 17β-estradiol 3-benzoate (EB); or diet admixed with 1000 ppm methoxychlor (MXC) or 10,000 ppm bisphenol A (BPA) for 20 weeks. Furthermore, additional groups were administered 200 ppm sulfadimethoxine (SDM) in the drinking water simultaneously with the BD, EB, MXC or BPA treatments. Thyroid follicular cell hyperplasias, adenomas and/or carcinomas were induced only in the EB+SDM group, the incidences of non-malignant lesions being significantly increased, as compared with the BD+SDM group values. Furthermore, the serum level of thyroid stimulating hormone (TSH) was significantly increased in this group. No significant variation in quantitative values for thyroid proliferative lesions or TSH levels were observed in the other treated groups. The results of the present study convincingly indicate that EB, with strong estrogenic activity, but not MXC and BPA, with weak estrogenic activities, exerts promoting effects on thyroid carcinogenesis in rats. The present modified rat two-stage thyroid carcinogenesis model appears to have advantages over our previous model for screening purposes.

Sex hormone modulation of serotonin-induced coronary vasodilation in isolated heart

The present study was designed to evaluate the differences in the coronary vasodilator actions of serotonin (5-HT) in isolated heart obtained from naive or castrated male and female rats that were treated with either estrogen or testosterone. Hearts from 12 groups of rats were used: male and female naive animals, castrated, castrated and treated with 17beta-estradiol (0.5 microg kg(-1) day(-1)) for 7 or 30 days, and castrated and treated with testosterone (0.5 mg kg(-1) day(-1)) for 7 or 30 days. After treatment, the vascular reactivity of the coronary bed was evaluated. Baseline coronary perfusion pressure (CPP) was determined and dose-response curves to 5-HT were generated. Baseline CPP differed between male (70 +/- 6 mmHg, N = 10) and female (115 +/- 6 mmHg, N = 12) naive rats. Maximal 5-HT-induced coronary vasodilation was higher (P<0.05) in naive female than in naive male rats. In both sexes, 5-HT produced endothelium-dependent coronary vasodilation. After castration, there was no significant difference in baseline CPP between hearts obtained from male and female rats (75 +/- 7 mmHg, N = 8, and 83 +/- 5 mmHg, N = 8, respectively). Castration reduced the 5-HT-induced maximal vasodilation in female and male rats (P<0.05). Estrogen treatment of castrated female rats restored (P<0.05) the vascular reactivity. In castrated male rats, 30 days of estrogen treatment increased (P<0.05) the responsiveness to 5-HT. The endothelium-dependent coronary vasodilator actions of 5-HT are greater in female rats and are modulated by estrogen. A knowledge of the mechanism of action of estrogen on coronary arteries could aid in the development of new therapeutic strategies and potentially decrease the incidence of cardiovascular disease in both sexes.

Comparison of the elimination between perfluorinated fatty acids with different carbon chain length in rats

Elimination in urine and feces was compared between four perfluorinated fatty acids (PFCAs) with different carbon chain length. In male rats, perfluoroheptanoic acid (PFHA) was rapidly eliminated in urine with the proportion of 92% of the dose being eliminated within 120 h after an intraperitoneal injection. Perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) was eliminated in urine with the proportions of 55, 2.0 and 0.2% of the dose, respectively. By contrast, four PFCAs were eliminated in feces with the proportion of less than 5% of the dose within 120 h after an injection. In female rats, the proportions of PFOA and PFNA eliminated in urine within 120 h were 80% and 51% of the dose, respectively, which were significantly higher compared with those in male rats. There was the tendency that PFCA with longer carbon chain length is less eliminated in urine in both male and female rats. Fecal elimination of PFCAs was not different between PFCAs in female rats and comparable to those in male rats. The rates of biliary excretion of PFCAs in male rats were slower than those in female rats. Sex-related difference in urinary elimination of PFOA was abolished when male rats had been castrated. On the contrary, treatment with testosterone suppressed the elimination of PFOA in urine in both castrated male rats and female rats. The effect of testosterone was in a time- and dose-dependent manner. These results suggest that PFCAs are distinguished by their carbon chain length by a renal excretion system, which is regulated by testosterone.

Modifying Effects of Endocrine Disrupting Chemicals on N-bis(2-hydroxypropyl) Nitrosamine and Sulfadimethoxine-Induced Thyroid Carcinogenesis in Rats.

To clarify whether 17β-estradiol 3-benzoate (EB), methoxychlor (MXC), atrazine (ATR), or bisphenol A (BPA) have any modifying effects on relatively late stages of thyroid carcinogenesis, six-week old female castrated F344 rats in Experiments 1 and 2 first received a single subcutaneous injection of 2000 mg/kg body wt of N-bis (2-hydroxypropyl) nitrosamine (DHPN) and, starting one week later, were given drinking water containing 1000 ppm sulfadimethoxine (SDM) for 8 weeks. Then, in Experiment 1, cholesterol pellets containing 0.5 mg EB were subcutaneously embedded and renewed every 4 weeks for 25 weeks. Controls received basal diet alone. In Experiment 2, rats of the control, MXC, ATR, or BPA group received diet containing no supplement, 1000 ppm MXC, 400 ppm ATR, and 10000 ppm BPA, respectively, for 27 weeks. Thyroid follicular cell hyperplasias, adenomas, and/or carcinomas were induced in all of the groups. In Experiment 1, the incidence of adenomas in the EB group was significantly increased, as compared to the corresponding control group value. In Experiment 2, the incidences of carcinomas in the MXC and BPA groups were significantly lower than in the corresponding control group. Serum estrogen levels and the PCNA labeling index for carcinomas in the EB group were significantly elevated but there was no clear alteration in serum thyroid related hormone levels. Serum T3 levels in the MXC and ATR groups were significantly reduced, whereas serum T4 was increased in these as well as the BPA group. No significant fluctuation in serum TSH levels was observed in these treated groups. The results of the present studies suggest that EB with strong estrogenic activity, but not MXC and BPA with only weak estrogenic activity or ATR, exerts promoting effects on thyroid carcinogenesis in rats.

Efeitos da Corticosteroidoterapia na Uretra e na Bexiga de Ratas Castradas antes e durante Reposição Estrogênica

Objetivo: avaliar os efeitos do uso de corticóides sobre os vasos e o epitélio da bexiga e da uretra de ratas. Método: utilizaram-se 54 ratas, divididas em 5 grupos: Grupo I - dez ratas castradas; Grupo II - onze ratas castradas que receberam succinato sódico de prednisolona, na dose de 15 mg/kg de peso, por via intraperitoneal durante 26 dias; Grupo III - doze ratas castradas que receberam o mesmo corticosteróide, na mesma dose associado ao 17 beta-estradiol na dose de 10 mg/kg, subcutâneo, nos últimos 5 dias antes de serem sacrificadas; Grupo IV - onze ratas castradas que receberam placebo por 26 dias; Grupo V - dez ratas não-castradas que receberam o mesmo corticosteróide, na dose e duração do grupo II. Resultados: observou-se na bexiga do grupo castrado que recebeu corticosteróide uma média de 1,8 vasos, número semelhante ao que recebeu corticosteróide e estrogênio, contra 0,8 vasos no grupo com placebo. Já na uretra, identificaram-se 0,7 vaso no grupo com corticosteróide, contra 0,9 vaso do grupo com corticosteróide associado ao estrogênio e 0,4 vaso no grupo placebo. Quanto à mucosa, observou-se que a espessura do epitélio vesical passou de 14,1 mm do grupo placebo para 20,6 mm no que recebeu corticosteróide e para 22,6 mm com corticosteróide e estrogênio. Da mesma maneira, a espessura do epitélio uretral passou de 12,4 mm no grupo controle para 15,1 mm no grupo com corticosteróide e para 16,7 mm com corticosteróide e estrogênio. Conclusões: a prednisolona, na dose e na duração utilizadas, aumentaram o número de vasos e a espessura do epitélio da bexiga e da uretra.

Relação tireóide-gônadas e níveis plasmáticos de fósforo, cálcio e fosfatase alcalina em ratas

A relação tireóide-gônadas-metabolismo ósseo foi estudada em ratas Wistar adultas, castradas ou intactas e mantidas em estado hipertireóideo ou eutireóideo por períodos de 30, 60 e 90 dias. Foram utilizadas como características do metabolismo ósseo o cálcio, o fósforo e a atividade da fosfatase alcalina plasmáticos, correlacionando-os com os valores de estrógeno, de progesterona e de T4 livre. Verificou-se que o hipogonadismo e o hipertireoidismo alteram as características plasmáticas do metabolismo ósseo. O hipertireoidismo induz hiperfosfatemia e hipocalcemia, o hipogonadismo tem pouca influência sobre o fósforo, mas potencializa a hiperfosfatemia e a hipocalcemia desencadeadas pelo hipertireoidismo. Com relação à fosfatase alcalina, conclui-se que o hipertireoidismo reduz o efeito do hipogonadismo sobre a atividade dessa enzima.