幼龄大鼠重复ig肠炎宁颗粒1个月毒性试验

目的 观察肠炎宁颗粒对幼龄大鼠可能引起的毒性反应和毒性靶器官,为临床应用提供参考。方法 雌性大鼠与雄鼠交配、受孕并生仔。从出生12 d的仔鼠中,筛选出128只（16窝,8只/窝）随机分入4组,每组每性别16只。仔鼠出生第13天,分别ig给予低、中、高剂量（2、4、8 g/kg）的肠炎宁颗粒,对照组给予去离子水,给药体积为10 mL/kg,连续给药31 d,分别于给药31 d和停药28 d次日剖杀。检测指标包括：一般症状、体质量、摄食量、睁眼、腹部出毛、空中翻正、自主活动、尿液、股骨长度、血液学、血清生化学、T淋巴细胞亚群、肉眼大体和镜下组织病理学检查。结果 与对照组比较,给药0~3 d,肠炎宁颗粒低、中、高剂量组雄鼠和低、高剂量组雌鼠的体质量增长、及高剂量组雌雄大鼠给药第3天体质量均明显降低（P<0.05、0.01）;给药31 d,中、高剂量组雄鼠平均股骨长度偏短（P<0.01）,高剂量组雌鼠红细胞（RBC）、血红蛋白（HGB）、红细胞容积（HCT）轻度降低（P<0.05）,给药组脾脏髓外造血增多;停药28 d后均恢复。未见与药物有关的其他不良反应。结论 本实验条件下,肠炎宁颗粒大剂量长期给药可引起幼龄大鼠出现一些异常反应,但程度轻微,且可恢复。     

Two-generation reproductive toxicity study of tributyltin chloride in female rats

A two-generation reproductive toxicity study of the effects of tributyltin chloride (TBTCl) was conducted in female rats using dietary concentrations of 5, 25, and 125 ppm TBTCl. Reproductive outcomes of dams (number and body weight of pups and the percentage of live pups) and the growth of female pups (the day of eye opening and body weight gain) were significantly decreased in the 125 ppm TBTCl group. A delay in vaginal opening and impaired estrous cyclicity were also observed in the 125 ppm TBTCl group. However, an increase in anogenital distance was found in all TBTCl groups on postnatal d 1. A dose-effect relationship was observed in TBTCl-induced changes in anogenital distance. These results indicate that the whole-life exposure to TBTCl affects the sexual development and reproductive function of female rats. In addition, the TBTCl-induced increase in anogenital distance seems to suggest it may exert a masculinizing effect on female neonates. However, the concentrations of TBTCl used in this study are not environmentally relevant.     

A dose-response study following in utero and lactational exposure to di(2-ethylhexyl)phthalate: effects on female rat reproductive development.

Phthalates, a class of chemicals used as plasticizers, are economically important due to several industrial applications. Di(2-ethylhexyl)phthalate (DEHP) is the most commonly used phthalate plasticizer, and it has been described as a potent antiandrogen in males. We performed an extensive dose-response study following developmental exposure to DEHP and evaluated the effects on female reproductive development. Two wide ranges of doses that included dose levels relevant for human exposure as well as high doses typically used in toxicological studies were tested. Female Wistar rats were treated daily with DEHP and peanut oil (vehicle control) by gavage from gestation day 6 to lactation day 22. The low doses were 0.015, 0.045, 0.135, 0.405, and 1.215 mg DEHP/kg body weight (bw)/day, and the high doses were 5, 15, 45, 135, and 405 mg DEHP/kg bw/day. At the dose levels tested, no signs of maternal toxicity were observed. A significant delay in the age at vaginal opening (approximately 2 days) at 15 mg DEHP/kg bw/day and above, as well as a trend for a delay in the age at first estrus at 135 and 405 mg DEHP/kg bw/day (approximately 2 days), was observed. Liver enlargement (characteristic of phthalate exposure in rats) was limited to the 135- and 405-mg DEHP/kg bw/day doses. Anogenital distance and nipple development were unaffected. Based on the results of delayed pubertal onset, the no observed adverse effect level for female reproductive development may be set at 5 mg DEHP/kg bw/day.     

Neurotoxic effects of 2,5-hexanedione on growing peripheral nerve axons of rat fetuses.

Peripheral nerves of rat fetuses were used to investigate the potential neurotoxicity of 2,5-hexanedione (2,5-HD) on developing axons. Pregnant female Sprague-Dawley rats were injected subcutaneously with 680 mg/kg of 2,5-HD once a day from day 12 of gestation (GD12) through GD16. On GD20 live fetuses were removed from the uterus, and the sciatic nerves were examined morphologically. Upon electron-microscopy affected nerves showed axons which were aggregated and fused together; the number of large axons was increased, but there were no axons aggregated with neurofilaments.     

Prenatal diclofenac exposure delays pubertal development and induces behavioral changes in rats

Diclofenac is a non-steroidal anti-inflammatory drug widely used by the general population and, although generally contraindicated during pregnancy, it is also used by some pregnant women. This study investigated endocrine, reproductive and behavioral effects of diclofenac in male and female offspring rats exposed in utero from gestational days 10–20. Pregnant rats were treated with diclofenac at doses of 0.2, 1 and 5 mg/kg/day via oral gavage. Anogenital distance (AGD), number of nipples, and developmental landmarks of puberty onset - vaginal opening (VO), first estrus (FE) and preputial separation (PPS) – were evaluated in the offspring. At adulthood, behavioral and reproductive parameters were assessed. Male and female rats were tested in the elevated plus maze test to assess locomotor activity and anxiety-like behaviors, while male rats were also evaluated in the partner preference test. No significant effects were observed on AGD and number of nipples in both males and females. Diclofenac treatment induced an overall delay in developmental landmarks of puberty onset in male and female offspring, which reached statistical significance for PPS at the lowest diclofenac dose. Prenatal exposure to all tested doses abolished the preference of male rats for an estrous female, suggesting an impairment of brain masculinization. No changes were observed on male or female reproductive parameters at adulthood. Overall, our results indicate that prenatal exposure to therapeutically relevant doses of diclofenac may have an impact in the pubertal development of rats and negatively affect male partner preference behavior.     

Ethanol-induced advance in the onset of puberty is prevented by the GABAA antagonist bicuculline in female rats

OBJECTIVE: The use of alcohol during lactation produces an advance in the onset of puberty in female rats. This research studied the possible participation of GABAA activity in this phenomenon. METHOD: Female Wistar rats were exposed to one of three different treatments from 13 to 18 days of postnatal age: (1) ethanol (2.5 g/kg PO) twice a day and isotonic saline (10 ml/kg IP) four times a day (AS group), (2) ethanol (2.5 g/kg PO) twice a day and bicuculline (2.5 mg/kg IP) four times a day (ABic group), (3) water (25 ml/kg PO) twice a day and bicuculline (2.5 mg/kg IP) four times a day (WBic group). A fourth group (control) did not receive any drug. RESULTS: The advance in the age at vaginal opening and at the first vaginal estrous seen in females of the AS group was completely prevented in the ABic group when bicuculline was added to alcohol treatment. The age at first behavioral estrous, however, was not different between groups. The age at vaginal opening, first vaginal estrous and first behavioral estrous was not significantly different in control, ABic and WBic groups. Body weight at vaginal opening was lower in the AS group than in the other three groups. Gestational period was longer in the AS group, but the number of pups per litter was lower in females of the ABic and WBic groups. CONCLUSIONS: The results reported here support a significant role for GABAA activity in the effects of alcohol at the onset of puberty.     

Chronic di-n-butyl phthalate exposure in rats reduces fertility and alters ovarian function during pregnancy in female Long Evans hooded rats.

Testis function in fetal and peripubertal male rats is disrupted by subchronic exposure to phthalate esters (PEs). In contrast to the male rat, it is generally held that reproduction in female rats is much less sensitive to phthalate-induced disruption. However, the current study demonstrates that oral administration of dibutyl phthalate (DBP) to female Long Evans (LE) hooded rats from weaning, through puberty, mating, and gestation disrupts pregnancy maintenance at dose levels similar to those that affect testis function in male rats. Administration of 500 and 1000 mg DBP/kg/day, but not 250 mg DBP/kg/day, to female LE rats induced midpregnancy abortions. The percentage of females delivering live pups was reduced by more than 50% at 500 mg/kg/day and by 90% at 1000 mg/kg/day in the absence of overt toxicity, whereas the ages at vaginal opening and first estrus, estrous cyclicity, and mating indices (N mated/N paired or N pregnant/N mated) were not significantly affected. On gestational day 13, prior to the stage when litters were being aborted, ex vivo ovarian hormone production was significantly decreased by in vivo DBP treatment at 500 and 1000 mg/kg/day. These results should be considered when evaluating mechanisms of reproductive toxicity for the PE because it is likely that these reproductive alterations in the female rat arise via a mode of action similar to that operative in male rats.     

Evidence for zinc protection against 2,5-hexanedione toxicity by co-exposure of rats to zinc chloride

The protective role of zinc against the toxic effects of 2, 5-hexanedione (2,5-HD), the main neurotoxic metabolite of n-hexane, was investigated by studying the interference of zinc on the toxicokinetics of 2,5-HD. Six groups of Wistar rats were exposed for 3 days to diets containing 2,5-HD, zinc chloride and 2,5-HD+zinc chloride. The amounts of pyrroles and free and total 2,5-HD in urine were determined using Ehrlichs's reagent and gas chromatography/flame ionization detection, respectively. The results show that after the first day of co-exposure (ZnCl(2)+2,5-HD) there was a significant decrease in the excretion of pyrroles and free 2, 5-HD in rats exposed to the chemical mixture when compared to the pyrroles and free 2,5-HD excreted in rats exposed to 2,5-HD alone. However, no significant decrease was observed in the urinary excretion of total 2,5-HD (free 2,5-HD + preformed 2,5-HD). Suggestions are made about the role played by this metal ion in inhibiting pyrrole formation.     

Effect of oral intake of dibutyl phthalate on reproductive parameters of Long Evans rats and pre-pubertal development of their offspring

To investigate the influence of dibutyl phtalate (DBP) given in a soy-free rat chow on pre-pubertal development, 46 Long Evans female rats 2-month-old were divided into three experimental groups and fed three different chows: (1) control; (2) DP 0.61 g/kg chow (12 mg/kgrat/day); (3) DP 2.5 g/kg chow (50 mg/kg rat/day) for 2 months. While under this treatment, they were mated and their offspring studied. Litter size and female:male ratio were recorded. At 14 days of age 6, male pups of each group were sacrificed and testis and thymus were excised and weighed. Pups were weaned at 22 days of age and continued into three experimental groups according to diet. From day 22 onwards, vaginal opening, occurrence of first estrous, and pre-putial separation were recorded. RESULTS: The percent of pregnancies showed a marked decrease in group 3, while no difference was observed between groups 1 and 2. Sex prevalence and litter size were not affected by the different diets. Pup survival showed a decrease when mothers were fed diet 2, but it was similar in diets 1 and 3. Pup weights on day 2 showed an evident (P < 0.05) reduction in groups 2 and 3, the decrease being more marked (P < 0.001) in group 3. On day 6, pups of group 2 showed lower weights (P < 0.01) as compared with the other groups. Weight gain was significantly higher in pups of group 3. Eye opening was not affected by the different diets. Fourteen-day-old male pups' relative weight of thymus and testis showed a decrease in animals whose mothers had been fed diets 2 and 3. Vaginal opening and occurrence of first estrous showed an evident delay (P < 0.05; P < 0.01) in females fed diets 2 and 3. Significant differences (P < 0.001) in pre-putial separation were observed between treated and untreated groups. Conclusion: Offspring pre-pubertal development seems to be affected by oral intake of DBP by their mothers during pregnancy, the effects being more evident in the reproductive development of male pups.     

Effects of peripubertal exposure to triphenyltin on female sexual development of the rat

Triphenyltin (TPT) belongs to the group of organotin compounds which have been shown to affect reproduction in mammals. It is used as a fungicide and antifouling agent and the main source of human exposure is via food. We studied the effects of 2 or 6 mg TPT/kg bw on female sexual development using a modification of the Rodent 20-Day Thyroid/Pubertal Female Assay. Moreover, the effect of TPT before the onset of puberty was investigated. Beginning at postnatal day (PND) 23 female Wistar rats were treated per gavage until either PND 33 or the first estrus after PND 53. A delay in the completion of vaginal opening (VO) was observed in the 6 mg TPT group, while the 2mg TPT group showed advanced VO. Significantly increased ovarian weights were observed in both treatment groups. Steroid hormone levels and ovarian aromatase activity were affected after exposure to 6 mg TPT/kg bw, while treatment with 2mg TPT/kg bw resulted in minor changes of these endpoints. We conclude that peripubertal exposure to 6 mg TPT/kg bw, and to a lesser extent to 2mg TPT/kg bw, affects female sexual development.     

Growth and development of male and female rats treated with the Leydig cell cytotoxin ethane dimethane sulphonate during the suckling period

The growth inhibiting effects of the Leydig cell cytotoxin ethane dimethane sulphonate (EDS) were investigated after treatment of both male and female neonatal rats. Pups were injected daily from day 4 to day 15 of age with EDS (50 mg/kg body weight sc), vehicle or water, or were not injected, according to a within-litter control experimental design. The rats were killed for necropsy at 40 and 80 days. The timing of attainment of the developmental milestones that appear during the suckling period was unaffected by treatment, but vaginal opening was 2 days later in EDS-treated females. After a delay of 9-10 days after the start of treatment the growth in body weight of both male and female EDS-treated rats was substantially and progressively depressed, such that by 80 days male and female EDS-treated rats showed body-weight deficits of 18 and 25%, respectively. The food intake of EDS-treated rats at 10 wk of age was less than that of controls, but was appropriate or more than appropriate for metabolic body size. As expected, testes were vestigial in EDS-treated males and the accessory male sexual organs were very small. Ovary and uterus weights were appropriate for body weight in EDS-treated females. At 80 days, liver weight was high for body weight in EDS-treated rats of both sexes. Possible mechanisms for the effect on body growth are discussed. Depressed food intake is discounted. Endocrine involvement, perhaps some anomaly of growth hormone release, or a more generalized toxic effect seem more likely.     

Effect of astragaloside IV on the general and peripartum reproductive toxicity in Sprague-Dawley rats

Fertility and early embryonic developmental toxicity in rats were evaluated by intravenously administering astragaloside IV (AS-IV) daily at 0.25, 0.5, and 1.0 mg/kg for 4 weeks before mating, throughout the mating period, and continuing to day 6 of gestation period in females. Perinatal toxicity in rats was evaluated on gestational days (GD) 15 to 21 and lactational days LD (LD) 1 to 21. Astragaloside IV had no maternal toxicity at 0.25 to 1.0 mg/kg in rats. Although it has an inhibitory effect on female fertility in F0/F1 rats, AS-IV was devoid of early embryonic developmental toxicity in F0/F1 rats and in the survival parameters of F1 postnatal rats. Maternal AS-IV exposure at the dose of 1.0 mg/kg per d resulted in a significant delay in time for fur development, eye opening, and cliff parry reflex of pups compared to control group (P < .05), whereas it did not affect the memory and learning of F1 pups.     

Effects of prepubertal exposure to forchlorfenuron through prenatal and postnatal gavage administration in developing Sprague-Dawley rats

Forchlorfenuron (CPPU), a plant growth regulator, is widely used in agriculture. However, its long-term exposure effects on humans, especially neonates, remain unclear. Therefore, we investigated the developmental toxicity of prenatal and postnatal gavage administration of CPPU in rats. Pregnant Sprague-Dawley rats were administered 300 mg/kg/day CPPU by gavage from day 6 of gestation to the cessation of nursing. During weaning, rat offspring were administered 0, 30, 100, or 300 mg/kg/day CPPU for 4 weeks, followed by a 4-week CPPU-free recovery period. There were no significant differences in clinical symptoms, body weight, development indicators, serum biochemical parameters, sex hormone levels, sperm motility, relative organ weights, and histopathological changes among the 0–100 mg/kg/day CPPU groups. In the 300 mg/kg/day CPPU group, female rats exhibited decreased body weight, earlier time of vaginal opening (VO) and first estrus time (FE), elevated estradiol and blood urea nitrogen (BUN) levels, and upregulation of estrogen receptor 1 gene expression, whereas male rats only exhibited increases in serum BUN, creatinine, and glucose levels. Most changes were reversed after the recovery period. Furthermore, the endometrial epithelial height was significantly increased in female rats despite the absence of significant changes in uterine wall thickness and endometrial glands. Thus, CPPU may promote estradiol secretion, resulting in altered VO and FE and adverse effects in prepubertal female rats. These findings may be applied for risk assessment following CPPU exposure in humans.     

Comparative effects of maternal prenatal and postnatal exposures to astemizole on reproductive parameters of rats

The prenatal and postnatal effects of administration of a nonsedative antihistamine H1, astemizole (ATZ), were compared. ATZ (10 mg/kg) was injected daily into female Wistar rats throughout pregnancy (prenatal treatment) or during the first 6 days of lactation (postnatal treatment). Neither treatment modified dam body weight. Prenatal exposure reduced offspring body weight and lead to a latter expression of the vaginal opening of female offspring. In addition, a long-term disruption of male reproductive behavior was observed, while female sexual behavior was not modified. The sexual activity index and the intromission frequency were increased in prenatally treated animals. Testes wet weight was reduced, but no modifications were detected in vas deferens or seminal vesicles. Postnatal treatment did not alter offspring body weight, open-field activity, sexual behavior and organ weight as well as did not delay testes descent but reduced the time until vaginal opening. Hypothalamic serotonin (5-HT), dopamine (DA) and noradrenaline (NA) as well as DA and NA metabolites were not modified by both prenatal and postnatal treatments. Increased striatal 3,4-dihydroxyphenylacetic acid (DOPAC) levels were observed after prenatal and postnatal treatments, while only postnatal 5-HT levels were increased. We propose that the present results indicate that prenatal ATZ exposure can have long-lasting organizational effects on reproductive behavior of male rats, while postnatal exposure to this drug did not alter mating behavior. In relation to female rats, prenatal and postnatal exposures to ATZ accelerated puberty but did not alter sexual behavior. Neurochemical data show that both treatments increased striatal dopaminergic system activity, suggesting a central ATZ effect after perinatal exposure.     

Reproductive outcomes in rat female offspring from male rats co-exposed to rosuvastatin and ascorbic acid during pre-puberty

Dyslipidemias are occurring earlier in different countries due to the increase of obesity, bad eating habits, and sedentary lifestyle. Rosuvastatin reduces serum cholesterol; however, several studies associated statin exposure with male reproduction impairment. Ascorbic acid (AA) is an antioxidant substance that plays a protective role in the male reproductive system. Male rats were randomly divided into 6 experimental groups (n = 10), which received saline solution 0.9%, 3 or 10 mg/kg/day of rosuvastatin, 150 mg/day of AA or 3 or 10 mg/kg/day of rosuvastatin associated with 150 mg/day of AA from post-natal day (PND) 23 until PND 53. On PND 100, males were mated with non-treated female rats to obtain the female pups. The day of vaginal opening and the first estrus were assessed in the offspring. Two sets of females were euthanized on the first estrus after PND 42 and PND 75 to evaluate the histology of reproductive organs and hormone levels. A third set was used for sexual behavior and fertility test around PND 75. Female offspring from males exposed or co-exposed to the higher dose of statin exhibited a lower number of corpora lutea during puberty. On sexual maturity, the experimental group from males that were exposed to 3 mg displayed lower uterine luminal epithelium area. Paternal exposure to rosuvastatin at pre-puberty diminished uterine luminal epithelium in female offspring suggesting epigenetic changes were initiated by statin. Ascorbic acid co-administered to pre-pubertal males was able to ameliorate the reproductive damage in rat female offspring in adulthood.     

The effects of simazine,a chlorotriazine herbicide,on pubertal development in the female Wistar rat

Chlorotriazine herbicides, such as atrazine and its metabolites, have been shown to target the neuroendocrine regulation of male and female reproductive development. However, no studies have evaluated the effects of the chlorotriazine simazine on pubertal development in the female rat. Here we report the effects of a 21- and 41-day exposure to simazine on pubertal development and estrous cyclicity in the female rat using the U.S. Environmental Protection Agency's Endocrine Disruptor Screening Program, Pubertal Development and Thyroid Function in Intact/Juvenile Peripubertal Female Rats (Tier 1) protocol. In the first study, Wistar rats were exposed orally to 0, 12.5, 25, 50, or 100 mg/kg of simazine from postnatal day 22 to 42. In the second study, rats were exposed from PND 22 until the first day of estrus after PND 62 to 0, 12.5, 25, 50, 100 or 200 mg/kg of simazine. In the 21-day exposure, vaginal opening (VO) was delayed, the number of normal cycles was significantly decreased, and the day of first estrus was delayed compared to controls. In the 41-day exposure, VO and the day of first estrus was delayed, but the number of normal estrous cycles was not different than controls. In addition, both studies showed a significant decrease in serum prolactin (PRL) following simazine exposure. This data clearly demonstrates that simazine delays the onset of puberty in the female rat and decreases serum PRL similar to other chlorotriazines. The extended dosing period after VO provides a sufficient time period to monitor the effects of a toxicant on estrous cyclicity, an important measure for reproductive competence.     

New NO-Donors with Antithrombotic and Vasodilating Activities,Part 14 1,3,4-Triazol-1-oles

Five 1,3,4-triazol-1-oles ( 5a—f ) with different alkyl, aryl, and arylalkyl substituents in 2,5-position were synthesized and tested for their antithrombotic properties. The 2,5-dimethyl derivative 5a was most active. 2 h after administration of 60 mg/kg to rats thrombus formation by a laser beam was inhibited by 42 % in arterioles and by 33 % in venules. At the same dose the blood pressure of SHR rats was slightly (5%) but significantly decreased even 4 h after application of 5a . This pattern of activities suggests a nitric oxide mediated mechanism of action. 1,1′-Azo-bis-ethanone oxime ( 7 ) — the synthetic precursor of 5a — inhibited the aggregation of blood platelet (Born test) with an IC₅₀ = 15 μmol/L.     

Methylphenidate reduces impulsive behaviour in juvenile Wistar rats, but not in adult Wistar, SHR and WKY rats

Rationale Impulsivity is a core symptom of attention deficit/hyperactivity disorder (ADHD). The spontaneously hypertensive rats (SHR) is a strain commonly used as an animal model of ADHD. However, there is no clear evidence that psychostimulants, which are used for treatment of ADHD, reduce impulsivity in SHR. Because ADHD mainly affects children, it may be relevant to study psychostimulants on juvenile animals. Objectives Using tolerance to delay of reward as index of impulsivity, the effects of methylphenidate were assessed in adult SHR, Wistar Kyoto (WKY) and Wistar rats and in juvenile Wistar rats. Materials and methods Animals were trained in a T-maze to choose between a small-but-immediate and a large-but-delayed reward. Adult SHR, WKY and Wistar rats were compared for their ability to tolerate a 15-s delay. The effect of methylphenidate on the tolerance to a 30-s delay was studied in adult rats of the three strains and in juvenile (4.5 to 6.5-week-old) Wistar rats. Results In adult rats, the waiting ability was lower in SHR than in control strains. Waiting ability was improved by methylphenidate (3 and 5 mg/kg) in juveniles, but not by methylphenidate (3 mg/kg) in adults. Conclusions These data support the idea that SHR are more impulsive than control strains. However, at the dose studied, methylphenidate fails to improve tolerance to delay in adult rats whatever the strain used. The reduction of impulsivity induced by methylphenidate in juvenile Wistar rats indicates that juvenile animals may be suitable for testing the therapeutic potential of drugs intended to the treatment of ADHD in children.     

The rate of 2,5-hexanedione intoxication, not total dose, determines the extent of testicular injury and altered microtubule assembly in the rat

Charles River CD rats (220 g) were intoxicated with 1.0, 0.5, or 0.25% 2,5-hexanedione (2,5-HD) in the drinking water for a total of 21, 35, or 69 days, respectively. All rats received a total dose of 131 +/- 2 mmol/kg 2,5-HD at dose rates ranging from 1.9 to 6.1 mmol/kg/day. Rats were sacrificed 4 weeks after ending intoxication to evaluate the extent of testicular injury. An exposure rate of 6.1 mmol 2,5-HD/kg/day produced uniformally low testis weights (49% of control) and severe germ cell depletion, while exposure at 1.9 mmol/kg/day gave normal testis weights and histology. Exposure at the intermediate dose rate of 3.8 mmol 2,5-HD/kg/day produced an intermediate degree of testicular injury. In a separate experiment, testis pyrrole content and microtubule assembly behavior were measured in rats exposed to 2,5-HD at the various dose rates for 3 weeks. The rate of intoxication determined the extent of biochemical abnormality. Rats exposed to 1.0, 0.5, or 0.25% 2,5-HD had microtubule nucleation times 55, 63, and 72% of control and pyrrole contents equivalent to 2.14, 1.40, and 1.18 nmol 2,5-dimethylpyrrole/mg testis protein. These data demonstrate that 2,5-HD-induced testicular injury, unlike the nervous system toxicity, is dependent upon the rate of intoxication independent of total dose.     

Modulation of mammary gland development in prepubertal male rats exposed to genistein and methoxychlor.

The estrogenic isoflavone genistein is a common dietary component that has been shown to affect reproductive development in experimental animals at high doses. The objective of the present study was to examine interactions of genistein and the hormonally active pesticide methoxychlor on mammary gland development in juvenile rats. Timed-pregnant Sprague-Dawley rats were fed a soy- and alfalfa-free diet containing different combinations of genistein (300 and 800 ppm) and methoxychlor (800 ppm). Rats were fed these diets starting on gestation day (GD)1 and continuing through pregnancy and lactation until postnatal day (PND) 22, when the pups were killed. Inguinal mammary glands from both female and male pups were processed as whole-mount preparations for morphometric analysis. The total glandular area and the numbers of branch points, lateral buds, and terminal end buds in the male rats were found to be significantly greater in the groups exposed to methoxychlor than those exposed to genistein only. These effects were not observed in the female rats. In the male rats, methoxychlor had the most prominent effect on elongating the glandular ducts, while genistein enhanced the ductile branching. The 2 compounds in combination promoted the development of alveolar-lobular structure, an effect not observed with either compound alone. Immunostaining for proliferating cell nuclear antigen revealed a high percentage of immunopositive cells in the mammary epithelia of the males exposed to methoxychlor and genistein (800 ppm) compared to the controls. While no significant changes in serum levels of mammotrophic hormones were detected, increased immunostaining for insulin-like growth factor-1 receptor, estrogen receptor alpha, and progesterone receptor in the genistein + methoxychlor group suggested that local factors involved in regulating mammary growth may have played a role in propagating the endocrine effects of these two compounds. These results indicated that the mammary glands of juvenile male rather than juvenile female rats may be more sensitive to certain endocrine-active compounds and that high levels of phytoestrogens have the potential to alter the toxicological behaviors of other hormone mimics.