Gastrointestinal absorption of cadmium in mice during gestation and lactation: II. Continuous exposure studies

The effect on cadmium retention of continuous exposure to drinking water containing low levels of cadmium during pregnancy and lactation was studied in mice. Female mice were provided drinking water ad libitum containing ¹⁰⁹CdCl₂ (0.03 μCi ¹⁰⁹Cd/ml, 0.11 ppb total cadmium) throughout either gestation, lactation, or a combined period of pregnancy and lactation. Nonpregnant control mice were exposed to the same cadmium solution for similar time periods. Dams in all three experimental groups retained two to three times more cadmium (expressed as percentage of ingested dose) than did nonpregnant controls. The ¹⁰⁹Cd contents of liver, kidney, mammary tissue, and duodenum increased strikingly in all three groups. Increases in kidney and mammary tissue were particularly apparent during lactation, with increases of fivefold for kidney and at least ninefold for mammary tissue, compared to levels in nonpregnant controls. Increases in ¹⁰⁹Cd retention by the duodenum were fivefold during gestation and three- to fourfold during lactation. The kidneys of dams exposed during lactation retained 53% of the whole body ¹⁰⁹Cd, while kidneys of nonpregnant controls retained only 27%. Results indicate that pregnant and lactating mice absorb and subsequently retain substantially more cadmium from their diets than do nonpregnant mice.     

Normal mammary gland morphology in pubertal female mice following in utero and lactational exposure to genistein at levels comparable to human dietary exposure

The objective of the study was to determine the effect of in utero and lactational exposure to genistein (0, 0.1, 0.5, 2.5 and 10 mg/kg/day) on mammary gland morphology in female B6D2F1 mice at levels comparable to or greater than human exposures. The effect of diethylstilbestrol (DES; 0, 0.1, 1, 10 microg/kg/day) on the mammary gland was also examined as a positive estrogenic control. Pregnant females were treated by daily gavage from gestational day 12 to postnatal day (PND) 20. Female offspring were weaned on PND21 and mammary gland whole mounts were examined for growth (length and area of the epithelial tree), proliferation (number of terminal end buds (TEBs)), and differentiation (density of alveolar buds (ABs)) on PND49. The highest dose of DES induced a significant increase in mammary gland growth (P<0.05) and also decreased the number of TEBs (P<0.06). The density of ABs was not significantly affected by DES. By contrast to DES, genistein had no effect on mammary gland morphology at any dose. These results suggest that in utero and lactational exposure to genistein at levels comparable to or greater than human exposures do not adversely affect mammary gland development in pubertal female B6D2F1 mice.     

Early life exposure to genistein and daidzein disrupts structural development of reproductive organs in female mice

In mice, exposure to isoflavones (ISO), abundant in soy infant formula, during the first 5 d of life alters structural and functional development of reproductive organs. Effects of longer exposures are unknown. The study objective was to evaluate whether exposure to a combination of daidzein and genistein in the first 10 compared to 5 d of life results in greater adverse effects on ovarian and uterine structure in adult mice. Thirteen litters of 8-12 pups were cross-fostered and randomized to corn oil or ISO (2 mg daidzein + 5 mg genistein/kg body weight/d) for the first 5 or 10 d of life. The 10-d protocol mimicked the period when infants are fed soy protein formula (SPF) but avoids the time when suckling pups can consume mother's diet. Body and organ weights, and histology of ovaries and uteri were analyzed. There were no differences in the ovary or uterus weight, number of ovarian follicles, number of multiple oocyte follicles, or percent of ovarian cysts with 5 or 10 d ISO intervention compared to respective controls. The 10-d ISO group had higher body weights from 6 d to 4 mo of age and a higher percent of hyperplasia in the oviduct than the respective control. Lower number of ovarian corpus lutea and a higher incidence of abnormal changes were reported in the uteri of both ISO groups compared to their respective controls. Five and 10-d exposure to ISO had similar long-lasting adverse effects on the structure of ovaries and uterus in adult mice. Only the 10-d ISO exposure resulted in greater body weight gain at adulthood.     

镉接触对妊娠期及哺乳期大鼠及仔代生长发育的影响

目的 观察妊娠期及哺乳期镉接触对大鼠性别分化、生长发育和青春期启动的影响,以及其可能的内分泌干扰机制。方法 SD雌性大鼠从妊娠第1天开始至仔鼠断奶,自由饮用含0、5、20和40mg/L氯化镉的水。结果 各剂量组仔鼠的生长发育、青春期启动均受到明显影响：出生后（PND）21d体重明显低于对照组;阴道开放、包皮分离比对照组延迟2－3d。但是,各剂量组对妊娠时间、羊床数、每胎活产数、性别比例、肛殖距离没有明显的影响。结论 在该实验条件下,并未显示镉具有雌激素样活性。镉可能通过多种机制,如甾类生成、甲状腺、垂体性腺轴等,干扰内分泌系统,从而影响大鼠的生长发育、青春期启动。     

Effects of dietary genistein exposure during development on male and female CD (Sprague-Dawley) rats

Genistein is a naturally occurring isoflavone that interacts with estrogen receptors and multiple other molecular targets. Human exposure to genistein is predominantly through consumption of soy products, including soy-based infant formula and dietary supplements. A dose range-finding study was conducted as a prelude to a multigeneration bioassay to assess potential toxicities associated with genistein consumption. Genistein was administered in a soy- and alfalfa-free diet at 0, 5, 25, 100, 250, 625, or 1250 ppm to pregnant dams starting on Gestation day 7 and continuing throughout pregnancy. Dietary exposure of the dams continued through lactation, and pups were maintained on the same dosed feed as their mother after weaning until sacrifice at Postnatal day 50. Body weight and feed consumption of the treated dams prior to parturition showed a decreasing trend with a significant reduction at the highest dose. Litter birth weight was depressed in the 1250 ppm dose group, and pups of both sexes in that dose group had significantly decreased body weights relative to controls at the time of sacrifice. The most pronounced organ weight effects in the pups were decreased ventral prostate weight in males at the 1250 ppm dose and a trend toward higher pituitary gland to body weight ratios in both sexes. Histopathologic examination of female pups revealed ductal/alveolar hyperplasia of the mammary glands at 250 to 1250 ppm. Ductal/alveolar hyperplasia and hypertrophy also occurred in males, with significant effects seen at 25 ppm and above. Abnormal cellular maturation in the vagina was observed at 625 and 1250 ppm, and abnormal ovarian antral follicles were observed at 1250 ppm. In males, aberrant or delayed spermatogenesis in the seminiferous tubules relative to controls was observed at 1250 ppm. There was a deficit of sperm in the epididymis at 625 and 1250 ppm relative to controls, although testicular spermatid head counts and epididymal spermatozoa counts did not show significant differences from controls at these doses. Both sexes showed an increase in the incidence and/or severity of renal tubal mineralization at doses of 250 ppm and above. Dietary genistein thus produced effects in multiple estrogen-sensitive tissues in males and females that are generally consistent with its estrogenic activity. These effects occurred within exposure ranges achievable in humans.     

Effects of lead (Pb) exposure during gestation and lactation on female pubertal development in the rat

Lead (Pb) can delay sexual maturation; however, the mechanism and critical time of insult are not clearly defined. Therefore, we assessed maternal Pb levels during low-level gestational and/or lactational exposure, as well as blood and tissue Pb in developing fetuses in relation to the subsequent detrimental effects of Pb on puberty-related hormones and the onset of female puberty. Adult Fisher 344 female rats were gavaged daily with either a 1-ml solution of PbAc containing 12 mg/ml Pb or an equal volume of sodium acetate (NaCl), for the controls, from 30 days prior to breeding until their pups were weaned at 21 days. By cross-fostering at the time of birth, the pups were either exposed to PbAc or NaAc during gestation only, lactation only, or during both gestation and lactation. Pb delayed the timing of puberty and this delay was associated with suppressed serum levels of insulin-like growth factor-1 (IGF-1), luteinizing hormone (LH), and estradiol (E(2)). Liver IGF-1 mRNA was not affected, suggesting that Pb altered translation and/or secretion of IGF-1. We reported previously that peripherally derived IGF-1 acts at the hypothalamic level to facilitate LH release at puberty; hence, we suggest that the action of Pb in decreasing circulating IGF-1 contributes to the delayed puberty. The detrimental effects occurred regardless of the developmental time of exposure, although gestational exposure appeared more sensitive to the effects of Pb. Also, the effects noted were with blood Pb levels less than previously reported and these levels are relevant to human health concerns.     

槲皮素对幼鼠卵巢发育以及血液中激素水平的影响

为了探讨槲皮素对3周龄小鼠卵巢发育和血浆中激素水平的影响,本研究使用槲皮素对3周龄小鼠进行连续灌胃(45、25和5 mg·kg-1.d-1)50天,定期监测发情周期和血液中相关激素水平变化;处死动物后取出卵巢进行组织形态分析,观察各级卵泡及其PCNA染色细胞的比例。结果显示,槲皮素组较空白对照组能增加卵巢的器官指数(P<0.05),能提高原始卵泡和次级卵泡的比例(P<0.05)并降低成熟卵泡、闭锁卵泡和黄体的比例(P<0.05),能有效提高各级卵泡中增殖细胞的比例(P<0.05),对于小鼠血液中各激素水平有较为明显的影响(P<0.05),尤其是卵泡刺激素(FSH)和黄体生成素(LH)。由此可见,槲皮素在小鼠卵巢发育阶段呈现出一定的类雌激素的性质,在幼鼠发育阶段长期摄入槲皮素,将影响其卵巢发育以及体内相关的激素水平。     

Cadmium pathways during gestation and lactation in control versus metallothoinein 1,2-knockout mice.

Effects of metallothionein (MT) on cadmium absorption and transfer pathways during gestation and lactation in mice were investigated. Female 129/SvJ metallothionein-knockout (MT1,2KO) and metallothionein-normal (MTN) mice received drinking water containing trace amounts of (109)CdCl(2) (0.15 ng Cd/ml; 0.074 micro Ci (109)Cd/ml). (109)Cd and MT in maternal, fetal, and pup tissues were measured on gestation days 7, 14, and 17 and lactation day 11. In dams, MT influenced both the amount of (109)Cd transferred from intestine into body (two- to three-fold higher in MT1,2KO than MTN dams) and tissue-specific (109)Cd distribution (higher liver/kidney ratio in MT1,2KO dams). Placental (109)Cd concentrations in MT1,2KO dams were three- and seven-fold higher on gestation days 14 and 17, respectively, than in MTN dams. Fetal (109)Cd levels were low in both mouse types, but at least 10-fold lower in MTN fetuses. MT had no effect on the amount of (109)Cd transferred to pups via milk; furthermore, 85-90% of total pup (109)Cd was recovered in gastrointestinal tracts of both types, despite high duodenal MT only in MTN pups. A relatively large percentage of milk-derived intestinal (109)Cd was transferred to other pup tissues in both MT1,2KO and MTN pups (14 and 10%, respectively). These results demonstrate that specific sequestration of cadmium by both maternal and neonatal intestinal tract does not require MT. Although MT decreased oral cadmium transfer from intestine to body tissues at low cadmium exposure levels, MT did not play a major role in restricting transfer of cadmium from dam to fetus via placenta and to neonate via milk.     

Protective role of zinc against the toxicity induced by exposure to cadmium during gestation and lactation on testis development

To assess the effects of exposure to Cd and Zn on rat testicular development, offspring, from mothers receiving either tap water, Cd, Zn or Cd + Zn during gestation and lactation periods, were observed on gestational day (GD) 20 and on postnatal days (PND) 12, 21 and 35. During gestation, Cd induced maternal hypozincemia and less transfer of Zn to the fetus. During lactation, progressive Cd accumulation and Zn depletion in testis at PND12 and PND21 were noted. An increase of abnormal seminiferous tubules and a decrease in testis weight and plasmatic testosterone concentration were also observed at PND21 and PND35 respectively. Interestingly, Zn supply induced a significant protection against Cd toxicity. These results suggest that the toxic effects of Cd observed during development are mediated by the disruption of Zn metabolism, which is established in mothers during pregnancy causing Zn deficiency in fetuses and continues to become more pronounced during lactation.     

Daily exposure to silver nanoparticles during prepubertal development decreases adult sperm and reproductive parameters

Abstract

As silver nanoparticles (AgNPs) have antimicrobial properties and potentiate the activity of some antibiotics, they are broadly used in both medical and nonmedical applications. In this study, prepubertal male Wistar rats were orally treated with 15 or 30?µg/kg/day AgNPs from postnatal day 23 (PND23) to PND58 and sacrificed at PND102. The acrosome integrity, plasma membrane integrity, mitochondrial activity and morphological alterations of the sperm were analyzed. Sexual partner preference, sexual behavior and the serum concentrations of FSH, LH, testosterone and estradiol were also recorded. The results were evaluated following the appropriate statistical analyses, and differences among the groups were considered significant when p?<?0.05. AgNPs reduced the acrosome and plasma membrane integrities, reduced the mitochondrial activity and increased the abnormalities of the sperm in both treatment groups. AgNP exposure also delayed the onset of puberty, although no changes in body growth were observed in either treatment group. The animals did not show changes in sexual behavior or serum hormone concentrations. This study shows for the first time that prepubertal exposure to AgNPs causes alterations in adult sperm parameters. Importantly, the sperm appeared to be more sensitive to the toxic effects of AgNPs and demonstrated adverse effects following exposure to lower doses. Consequently, the effects of AgNPs on sperm should be considered in order to establish safety limits for the use of these particles.     

Maternal nicotine exposure during gestation and lactation induces cardiac remodeling in rat offspring

The aim of this study was to evaluate the effects of maternal nicotine exposure on heart morphology and fibrosis in rat offspring. Nicotine was administered to pregnant Sprague-Dawley rats by using a subcutaneous osmotic mini-pump at a dose of 6 mg/kg/day from Gestational Days 7–21 or Gestational Day 7 to Postnatal Day 14. A control group received an equal volume of saline by the same route as nicotine. Rats born to prenatal nicotine-treated dams exhibited significantly greater cell width of cardiomyocytes, fewer cardiomyocyte nuclei number, higher β-myosin heavy chain and transforming growth factor (TGF-β1) expression, and higher collagen deposition in heart compared with rats born to normal saline-treated dams on Postnatal Days 7 and 21. Postnatal nicotine exposure further enhances these effects. We conclude that TGF-β1 may be involved in the pathogenesis of cardiac remodeling induced by maternal nicotine exposure during gestation and lactation in rat offspring.     

The effects of exposure to diazepam during various stages of gestation or during lactation on the development and behavior of rat pups

In the present study we have investigated the effects of diazepam (DZP) (10 mg/kg) treatment of rat dams during different periods of gestation or during lactation on the development and behavior of their offspring. The results show that DZP exposure during different phases of early development has differing effects on later behavior. Exposure during mid-gestation resulted in early and transient hyperactivity, but no learning or memory deficits at 2 months of age were observed. However, both late prenatal and early postnatal exposure to DZP resulted in significant behavioral changes. Late prenatal treatment caused no hyperactivity but resulted in poor performance on the learning and retention of a choice discrimination task, while early postnatal exposure resulted in consistent and lasting hyperactivity and in substantial discrimination learning and retention deficits at 2 months of age.     

Lead exposure reduces sperm quality and DNA integrity in mice

Toxicity of lead on male reproductive functions has raised wide public concern as environmental lead contamination remains common worldwide. Conflicting and controversial data are available regarding effects of lead on male fertility. More importantly, our knowledge on effects of lead on sperm DNA integrity is significantly limited. Thus, further studies should focus on this issue. In the current study, adult male mice were exposed to a series of lead acetate concentrations in drinking water for six weeks. Following administration, lead levels in blood, testicles, and epididymis were measured, and potential changes in morphology of testis and epididymis due to lead exposure were identified. We also analyzed sperm parameters, including sperm density, viability, motility, and morphology, to evaluate quality of sperm collected from epididymis. Especially, hypothetical influence of lead on sperm DNA integrity was also evaluated by terminal deoxynucleotidyltransferase‐mediated dUTP‐biotin nick end labeling, alkaline comet assay, and sperm chromatin structure assay. Lead exposure possibly exerted no effect on growth of mice because these animals acquired similar body weight gain during the experimental period. However, high lead concentrations (0.5% and 1%) in drinking water affected sperm motility and increased percentage of spermatozoa with abnormal morphology. In groups treated with 0.25%, 0.5%, and 1% lead acetate, percentages of sperm cells showing DNA breaks and chromatin structure damage significantly increased. Altogether, lead exposure not only exhibits adverse effects on sperm physiological parameters, but also impairs DNA structure and integrity. These effects may lead to significant decline in male fertility.     

Self-administration of heroin in rats: effects of low-level lead exposure during gestation and lactation

Rationale Developmental lead exposure has been found to produce differential patterns of drug self-administration in adult animals.Objectives The present study examined the effects of perinatal (gestation/lactation) lead exposure on adult patterns of heroin self-administration.Methods Female rats were gavaged daily with 0 mg or 16 mg lead for 30 days prior to breeding with non-exposed males. Metal administration continued through pregnancy and lactation and was discontinued at weaning [postnatal day 21 (PND 21)]. Animals born to control or lead-exposed dams received indwelling jugular catheters as adults and were randomly assigned to one of two studies. In experiment 1, animals were tested on a FR-2 schedule in an effort to examine differential sensitivity to heroin in an intravenous self-administration paradigm. Seven doses of heroin were selected ranging from 0.56 g/kg to 36 g/kg per infusion. In experiment 2, littermates were tested on a progressive ratio (PR) schedule in order to more explicitly determine the nature of the change in sensitivity to the drug.Results In experiment 1, lead-exposed animals responded for heroin at significantly lower rates across most doses as evidenced by a downward shift in the inverted-U dose–effect curve. Congruent with these findings, lead-exposed animals in experiment 2 exhibited a decrease in progressive ratio responding (lower breaking points) across all heroin doses, further suggesting that perinatal lead exposure attenuates opiate self-administration in adult animals by altering the rewarding efficacy of the drug. In experiment 2, it was determined further that lead-exposed animals had lower latencies to make the initial lever press for heroin.Conclusions These results support previous literature suggesting that perinatal exposure to inorganic lead attenuates the effectiveness of opiates as a reinforcer when animals are tested in the adult life cycle.     

Decline of sperm quality and testicular function in male mice during chronic low-dose exposure to microcystin-LR

The effects of chronic low-dose exposure to microcystins were preliminarily studied on sperm quality and testicular function in male mice. Microcystin-LR (MC-LR) was orally administered to male mice at 0, 1, 3.2, and 10 μg/L for 3 and 6 months. Our preliminary study found in three-month group, sperm quality declined at 3.2 and 10 μg/L doses, testosterone dropped at 10 μg/L, levels of LH and FSH increased, and Leydig cells exhibited apoptosis. Similar, but more pronounced, effects were observed in groups treated with MC-LR for 6 months. Compared to control (0 μg/L), the rate of sperm abnormality was higher and testosterone levels were lower following administration of 3.2 and 10 μg/L MC-LR and structural damage to the testis was observed with 10 μg/L dose. Thus, chronic low-dose treatment with MC-LR results in substantial toxicity to male reproduction, causing declines in sperm quality, decreased levels of serum testosterone, and injury to the testis.     

Effect of low dose of vinclozolin on reproductive tract development and sperm parameters in CD1 outbred mice

The effect of a low dose of vinclozolin within the development of the reproductive tract during gestation (VIN-GD 15–22) and puberty (VIN-PND 23–44) in CD1 mice was tested. We found a decrease in the anogenital distance, prostate weight and pathology of testes in both experimental groups. Sperm counts decreased to 46% (VIN-GD) and to 81% (VIN-PND), and also the acrosomal state (evaluated by antiacrosomal antibody) decreased in both groups to 89% in comparison to the control group (100%). Sperm head abnormalities increased by approximately 18% and 13%, respectively. In this connection, the expression of some genes was changed (arosome-related gene (Acr), apoptosis related genes (p53, p21)). In conclusion, a low dose of vinclozolin affected the reproductive tract, sperm parameters and expression of selected genes in both experimental groups.     

Neurobehavioral effects in offspring of mice given excess aluminum in diet during gestation and lactation

Aluminum (Al) as Al lactate in a purified diet (25, 500 or 1000 micrograms Al/g diet) was fed to Swiss-Webster mice from conception through weaning. Weights, food intake and toxic signs were recorded at regular intervals and pregnancy outcome evaluated. Pups were assessed for growth, neurobehavioral development and toxic signs prior to weaning. Offspring were also evaluated with a multi-item neurobehavioral test battery immediately after weaning and again after a 2-week period during which they were all fed control (25 micrograms/g Al) diet. No maternal or reproductive toxicity was detected and there were no group differences in pup mortality, growth, toxic signs, or neurobehavioral development prior to weaning, with the exception of poor performance in a climbing test in the 1000 micrograms Al/g diet group. Parameters significantly affected by Al in the postweaning neurobehavioral testing were foot splay, forelimb and hindlimb grip strengths, and thermal sensitivity. Negative geotaxis was inconsistently affected and startle responses were not affected. These results show that maternal dietary exposure to excess Al during gestation and lactation which do not produce maternal toxicity can result in persistent neurobehavioral deficits in weanling mice.     

Impact of dietary exposure to methoxychlor, genistein, or diisononyl phthalate during the perinatal period on the development of the rat endocrine/reproductive systems in later life

To evaluate the impact of dietary exposure to endocrine disrupting chemicals (EDCs) during the sensitive period of brain sexual differentiation, maternal Sprague-Dawley rats were fed three representative chemicals, methoxychlor (MXC; 24, 240, and 1200 ppm), genistein (GEN; 20, 200, and 1000 ppm), or diisononyl phthalate (DINP; 400, 4000, and 20,000 ppm), from gestational day 15 to postnatal day 10. Soy-free diet was used as a basal diet to eliminate possible estrogenic effects from the standard diet. Offspring were examined in terms of anogenital distances, prepubertal organ weights, onset of puberty, estrous cyclicity, and organ weights and histopathology of endocrine organs at adult stage (week 11) as well as the volumes of sexually dimorphic nucleus of preoptic area (SDN-POA). All chemicals caused signs of maternal toxicity at high doses. MXC, at 1200 ppm, facilitated and delayed the onset of puberty in females and males, respectively, females also showing endocrine disrupting effects thereafter, such as irregular estrous cyclicity and histopathological alterations in the reproductive tract and anterior pituitary. GEN, at all doses, reduced body weight (BW) at week 11, but did not affect endocrine parameters. Treatment with DINP at 20,000 ppm resulted in degeneration of meiotic spermatocytes and Sertoli cells in the testis and decrease of corpora lutea in the ovary at week 11, although changes remained minimal or slight. The SDN-POA volume remained unchanged with all three chemicals. The results demonstrated that perinatal dietary exposure to EDCs for a limited period causes endocrine disruption in offspring only at high doses.