Lead-induced changes in ovarian follicular development and maturation in mice

The Association between Lead Exposure and Bone Mineral Density in Childhood and Adolescence: Results from NHANES 1999-2006 and 2011-2018

There are few studies on lead's effect on bone mineral density (BMD) in childhood. In this study, we examined the association between lead exposure and BMD among 13,951 children and adolescents aged 8-19 years from NHANES 1999-2006 and 2011-2018. The whole blood lead levels (BLLs) were used as lead exposure biomarkers, and total BMD, subtotal BMD, lumbar spine BMD and limb BMD were used as outcome variables. The survey weighted multivariable generalized additive models (GAMs) with smoothing terms were used to explore the association between blood lead levels and BMDs, adjusted for age, sex, race/ethnicity, height, weight, family-income-to-poverty ratio and blood cadmium. Subgroup analyses stratified by sex and bony sites were further performed. We found an N-shaped curve association between BLLs and total BMD, subtotal BMD and limb BMD for males and females, whereas the association between BLLs and lumbar spine BMD was only significantly negative for females. The findings suggested that lead exposure had different effects on BMD of different bony sites (highly cortical or trabecular regions) in childhood and adolescence and had different effects on the same bone among different ages population and/or at different levels.

The associations among lead exposure, bone mineral density, and FRAX score: NHANES, 2013 to 2014

Lead exposure has been suspected as a risk factor for osteoporosis. However, in epidemiological studies, the association between environmental lead exposure and bone health were inconsistent. With the decrease of lead exposure in recent decades, we evaluated the association between lead exposure and bone mineral density (BMD) in the general US population in this study. We analyzed data on 1859 adults (aged ≥40 years) from the National Health and Nutrition Examination Survey (NHANES) conducted in 2013-2014 to determine the relationship among lead exposure measured by both blood and urine lead concentration, BMD of total spine and femur, and FRAX score in a cross-sectional study. In premenopausal women, the results showed a 1-unit increase in natural log-transformed blood and urine lead levels was associated with a decrease in total femur BMD of 0.061 g/cm² (S.E. = 0.015; p = 0.001) and 0.046 g/cm² (S.E. = 0.018; p = 0.020), respectively. Moreover, in premenopausal women, a 1-unit increase in natural log-transformed blood level was associated with a decrease in total spine BMD of 0.054 g/cm² (S.E. = 0.019; p = 0.013). Both FRAX scores were positively correlated with blood and urine lead levels in subjects without fractures, while the 10-year hip fracture risk score was positively associated with lead exposure in subjects with a history of fracture or vertebral fracture. In conclusion, lead exposure was associated with decreased total femur and spine BMD, and FRAX score in the general US population. Further research is needed to elucidate the causal relationship among lead exposure, BMD, and fracture risk.

The effects of exposure to lead, cadmium and mercury on follicle-stimulating hormone levels in men and postmenopausal women: data from the Second Korean National Environmental Health Survey (2012-2014)

Background

Follicle-stimulating hormone (FSH), a gonadotropin secreted by the pituitary gland, is a representative secondary sex hormone and an important indicator of reproductive function. The effects of heavy metals such as lead, cadmium, and mercury on humans have been studied, but reports on their effects on sex hormone levels are lacking. Therefore, we investigated the relationship between heavy metal exposure and FSH levels in Korean men and postmenopausal women.

Methods

A total of 4,689 adults (2,763 men and 1,926 postmenopausal women aged 50 years or over) who participated in the Second Korean National Environmental Health Survey (2012–2014) were included. We compared differences in serum FSH levels by demographic characteristics using the t-test and analysis of variance. Multiple linear regression analysis was used to determine the relationship between the blood levels of lead and mercury and the urine cadmium level, and serum FSH levels.

Results

On multiple linear regression analysis, lead exposure was positively associated with serum FSH concentrations in postmenopausal women (β = 2.929, p = 0.019). However, we found no significant association between serum FSH concentration and blood lead and mercury levels, or urine cadmium level, in men.

Conclusions

This study suggests that lead exposure can affect the FSH level in postmenopausal women. Further studies are needed to evaluate the effects of low-dose long-term exposure to heavy metals on sex hormones.

Intrauterine, Infant, and Childhood Factors and Ovarian Reserve in Young African American Women

Background: Ovarian toxic exposures during early development may contribute to reduced ovarian reserve in adulthood. Materials and Methods: We explored a range of intrauterine, infant, and childhood factors in relation to a biomarker of ovarian reserve, anti-Müllerian hormone (AMH) concentrations, in adulthood. We conducted a cross-sectional exploratory study of 1600 African American women 23-35 years of age residing in the Detroit, Michigan metropolitan area, who had serum AMH measurements (Ansh Labs PicoAMH enzyme-linked immunosorbent assay) and no previous polycystic ovarian syndrome diagnosis. Information on 32 intrauterine, infant, and childhood factors was ascertained by self-administered questionnaires, with 87% of participants receiving assistance from mothers. The percent differences in AMH concentrations in relation to early-life factors and 95% confidence intervals (CIs) were estimated using multivariable linear regression, adjusting for age, current hormonal contraceptive use, and body mass index. Results: Of the early-life factors evaluated in this study, two maternal pregnancy factors were associated with lower AMH concentrations in adult participants. Participants whose mothers lived or worked on a farm (vs. neither lived nor worked on a farm) when pregnant with the participant had 42% lower AMH concentrations (95% CI = -62 to -9). Among participants whose mothers lived in Michigan when pregnant with the participant (n = 1238), maternal residence in Detroit for at least a month was associated with 22% lower AMH concentrations (95% CI = -34 to -8) in the participant. Conclusions: Further research is merited to replicate our findings and identify the aspects of maternal farm exposure and Detroit residence that may be associated with lower AMH concentrations.

Toxicological effects and ultrastructural changes induced by lanthanum and cerium in ovary and uterus of Wistar rats

Rare earths have been widely used in a huge number of areas in industry and medicine. Therefore, they exist in the environment and possibly accumulated within the human body. However their effects in the living organism particularly in the female reproductive system are still unclear. In this work, the subcellular behavior of lanthanum and cerium was investigated through the Transmission Electron Microscopy (TEM), in different territories of the reproductive system of Wistar rats exposed intraperitoneally to soluble solution of these elements during 2 weeks. Ultrastructural investigations of ultrathin sections from uterus and ovary of treated rats revealed the existence of inclusions with high electron density and heterogeneous aspects in the lysosomes of uterus and ovary cells. Many disruptions of architecture were observed, accompanied with several changes like vacuolations, significant expansion of the endoplasmic reticulum, mitochondrial alterations and necrotic cells, demonstrating the toxicity of these elements with doses used. Phagolysosomes as well as eosinophils were also seen. Our experimental investigations revealed no intralysosomal inclusions in ultrathin sections of the uterus and ovary of pregnant control females. The original mechanism implicated in this insolubilization-concentration phenomenon of these elements, as non-soluble phosphate form, in the lysosomes is a biochemical one involving intralysosomal hydrolytic enzymes, the acid phosphatase.

Punicalagin Mollifies Lead Acetate-Induced Oxidative Imbalance in Male Reproductive System

Punicalagin (PU) is a known antioxidant. The present study examined PU to protect against lead-induced oxidative stress (OS) testicular damage in mice. Significant increase in lipid peroxidation (LPO) after intraperitoneal injection of lead acetate (LA) indicated enormous generation of reactive oxygen species (ROS). Lead-induced OS has a direct effect on the differentiation of spermatogonial cells, showing a significant decline in sperm count. Supplementation of PU significantly changes values of LPO and glutathione (GSH) with a concomitant increase in sperm count, a marked decrease in the abnormal sperms, and a decline in the morphologically abnormal sperm population. Moreover, the histopathological evaluation of testes and epididymides showed severe changes in mice treated with LA. PU significantly induced nuclear factor erythroid-2 related factor 2-like 2 (Nrf2) expression and phase II enzymes, and data suggest that PU may inhibit OS through Nrf2 activation. The fertility test proved that PU might play an important role in male infertility treatment, especially in the type of infertility induced by OS.

Effect of long-term dietary lead exposure on some maturation and reproductive parameters of a female Prussian carp (Carassius gibelio B.)

Lead is reported to be an endocrine disruptor. In the current study, we exposed female Prussian carp to artificial feed, supplemented with five doses of dietary Pb (0, 1 (control), 8, 13, 24, and 49 mg/kg) over either a 24-month period or a 12-month period, followed by further 12 months where the fish were fed the control diet. Periodically, oocyte maturation, gonadosomatic index (GSI), ability to secret luteinizing hormone (LH) as well as gonad Pb concentrations were measured. It was found that the reproductive system of the female Prussian carp is not indifferent to chronic exposure to lead. The negative effect was manifested by a decrease in the GSI after 12 months despite the fact that a higher proportion of oocytes at more advanced maturity stages were concurrently observed. After 12 months of exposure, the effect on LH secretion varied according to the dose. In the group exposed to the lowest dose (8 mg/kg), LH decreased spontaneously, and in the groups exposed to the highest two doses (24 and 48 mg/kg), a significantly higher LHRH-A-stimulated LH secretion was observed. After 24 months of lead exposure, the effects on oocyte maturation and size and on GSI values were not pronounced. Analysis of the effect of lead exposure on LH secretion showed that the relationships were similar to those observed after 12 months but nonsignificant. During chronic a 24-month period exposure to Pb, Prussian carp female appears to acclimate to Pb doses used in the experiment. After 12 months of exposure and 12 months of depuration, the levels of spontaneous and stimulated LH secretion observed in all the groups were similar to the control, which is evidence that depuration eliminates the previously observed effects of exposure to lead. Lead is easily accumulated in the ovary, reaching a fivefold higher level (0.8 mg/kg tissue) compared to the control(0.15 mg/kg tissue), but after discontinuation of exposure, this organ is quickly depurated. The results indicate that environmental Pb can be a potent endocrine disruptor affecting ovarian steroidogenesis, gametogenesis, and ovulation, which may lead to adverse impacts on fish reproduction and population density and that female Prussian carp become resistant to the negative effects of lead with advancing age, and their organs cope by reaching a state of homeostasis.

The association between cadmium, lead and mercury blood levels and reproductive hormones among healthy, premenopausal women

BACKGROUND

Cadmium, lead and mercury have been identified in human follicular fluid and ovarian tissue, and have been associated with adverse reproductive outcomes in epidemiologic studies; however, few studies have examined the relationship between blood metal levels and reproductive hormones.

METHODS

Among 252 premenopausal women aged 18-44 years, we examined the association between blood metal levels (cadmium, lead and mercury), cycle length, and reproductive hormones [FSH, LH, estradiol (E(2)) and progesterone] measured at clinically relevant time points in the menstrual cycle. The association between metal levels (continuous) and hormone levels was assessed using linear regression with hormone levels (natural) log transformed and the results interpreted as the percentage difference in hormone level per unit increase in metal level.

RESULTS

Median (interquartile range) cadmium, lead and mercury levels were 0.30 µg/l (0.19, 0.43), 0.87 µg/dl (0.68, 1.20) and 1.10 µg/l (0.58, 2.10), respectively. Each 1 µg/l increase in cadmium levels was associated with a 21% [95% confidence interval (CI): -2.9, 49.9] increase in early follicular phase E(2) levels after adjusting for age, race/ethnicity, lead and mercury. This association decreased when restricted to never smokers (10%; 95% CI: -19.5, 51.3). Cadmium was also associated with a non-significant 9% (95% CI: -0.2, 19.9), or 2.7 day, increase in cycle length among never smokers. No associations were observed between lead or mercury and the outcomes in adjusted analyses.

CONCLUSIONS

Further evaluation of the association between cadmium, E(2) and cycle length is warranted, taking into consideration cigarette smoke and its multiple components.

The relationships between blood lead levels and serum follicle stimulating hormone and luteinizing hormone in the National Health and Nutrition Examination Survey 1999-2002

The relationships between blood lead levels and serum follicle stimulating hormone and luteinizing hormone were assessed in a nationally representative sample of women, 35-60 years old, from the National Health and Nutrition Examination Survey 1999-2002. The blood lead levels of the women ranged from 0.2 to 17.0 μg/dL. The estimated geometric mean was 1.4 μg/dL, and the estimated arithmetic mean was 1.6 μg/dL. As the blood lead level increased, the concentration of serum follicle stimulating hormone increased in post-menopausal women, women who had both ovaries removed, and pre-menopausal women. The concentration of luteinizing hormone increased as blood lead level increased in post-menopausal women and women who had both ovaries removed. The lowest concentrations of blood lead at which a relationship was detected were 0.9 μg/dL for follicle stimulating hormone and 3.2 μg/dL for luteinizing hormone. Lead may act directly or indirectly at ovarian and non-ovarian sites to increase the concentrations of follicle stimulating hormone and luteinizing hormone.

Effects of exposure to heavy metals on viability, maturation, fertilization, and embryonic development of buffalo (Bubalus bubalis) oocytes in vitro

The aim of the present study was to examine the effect of heavy metals, cadmium and lead, on buffalo oocyte viability and in vitro development. Oocytes were aspirated from ovaries of slaughtered buffaloes. Only viable and metabolically active oocytes with more than three layers of cumulus cell layers and homogeneous ooplasm were selected. Effects of nine concentrations (0, 0.005, 0.05, 0.5, 1.0, 1.5, 2.5, 5, and 10 microg/mL) of cadmium or lead on buffalo oocyte viability, morphological abnormities, maturation, and embryonic development in vitro were studied. Oocytes were cultured for 24 h and then checked for viability (0.05% trypan blue staining for 2 min), morphological abnormalities, and reduction assay by MTT test in experiment 1. The doses of cadmium and lead causing 100% oocyte death (1-day culture) were determined (experiment 2). In experiment 3, viable oocytes were matured in vitro in media containing different levels of cadmium or lead and then inseminated in vitro with frozen-thawed spermatozoa, and the resultant cleaved embryos were cultured in a control embryo culture medium for 8 days. In experiment 4, oocytes were cultured in control oocyte maturation medium, then fertilized, and the resultant embryos were cultured in media containing different levels of cadmium or lead for 8 days. The number of cells in the trophectoderm and inner cell mass (ICM) and the total cell counts (TCN) of blastocysts derived by in vitro culture of two- to four-cell-stage embryos (produced in control medium) in media containing 0, 0.005, 0.05, 0.5, and 1.0 microg/mL of cadmium or lead were analyzed by differential staining technique (experiment 5). Cadmium and lead were found to have a dose-dependent effect on viability, morphological abnormities, maturation, cleavage and morula/blastocyst yield, and blastocyst hatching. A significant decline in viability of oocytes was observed at 1.0 mg/mL cadmium or lead compared to the control group. The doses of cadmium and lead causing 100% oocyte death (1-day culture) were 18 and 32 microg/mL, respectively. Cadmium and lead at 1.0 and 2.5 microg/mL, respectively, caused a significant reduction of maturation of oocytes compared to the lower concentrations. No cleavage or morulae/blastocysts were produced when the oocytes/embryos were cultured in media containing 2.5 and 5.0 mg/mL of either cadmium or lead, respectively. Similarly, no morulae/blastocysts were produced from cleaved embryos cultured in media containing 2.5 and 5.0 microg/mL cadmium and lead, respectively. The developmental block, degeneration, and asynchronous divisions were higher in embryos exposed to cadmium than in those exposed to lead. TCN and number of cells in ICM were significantly lower in blastocysts derived from two- to four-cell-stage embryos cultured in media containing heavy metals. In conclusion, cadmium and lead lowered the viability and development of buffalo oocytes but at a concentration higher than that estimated in the body fluids and environment. Cadmium was found to be more ovotoxic than lead.

Effects of inorganic lead on Western fence lizards (Sceloporus occidentalis)

Although anthropogenic pollutants are thought to threaten reptilian species, there are few toxicity studies on reptiles. We evaluated the toxicity of Pb as lead acetate to the Western fence lizard (Sceloporus occidentalis). The acute lethal dose and sub-acute (14-day) toxicity studies were used to narrow exposure concentrations for a sub-chronic (60-day) study. In the sub-chronic study, adult and juvenile male lizards were dosed via gavage with 0, 1, 10 and 20 mg Pb/kg-bw/day. Mortality was limited and occurred only at the highest dose (20 mg Pb/kg-bw/d). There were statistically significant sub-lethal effects of 10 and 20 mg Pb/kg-bw/d on body weight, cricket consumption, organ weight, hematological parameters and post-dose behaviors. Of these, Pb-induced changes in body weight are most useful for ecological risk assessment because it is linked to fitness in wild lizard populations. The Western fence lizard is a useful model for reptilian toxicity studies.

The effects of metals as endocrine disruptors

This review reports current knowledge regarding the roles that cadmium (Cd), mercury (Hg), arsenic (As), lead (PB), manganese (Mn), and zinc (Zn) play as endocrine-disrupting chemicals (EDCs). The influence of these metals on the endocrine system, possible mechanisms of action, and consequent health effects were correlated between experimental animals and humans. Analysis of the studies prompted us to identify some critical issues related to this area and showed the need for more rigorous and innovative studies. Consequently, it was recommended that future studies need to: (1) identify the mechanisms of action, because at the present time only a few have been elucidated-in this context, the possible presence of hormesis need to be determined, as currently this was reported only for exposure Cd and As; (2) study the possible additive, synergistic, or antagonistic effects on the endocrine system following exposure to a mixture of metals since there is a lack of these studies available, and in general or occupational environments, humans are simultaneously exposed to different classes of xenobiotics, including metals, but also to organic compounds that might also be EDCs; (3) assess the potential adverse effects on the endocrine system of low-level exposures to metals, as most of the information currently available on EDCs originates from studies in which exposure levels were particularly high; and (4) assess the effects on the endocrine and reproductive systems of other metals that are present in the general and occupational environment that have not yet been evaluated.

The effect of lead intoxication on endocrine functions

Studies on the effects of lead on the endocrine system are mainly based on occupationally lead-exposed workers and experimental animal models. Although evidence is conflicting, it has been reported that accumulation of lead affects the majority of the endocrine glands. In particular, it appears to have an effect on the hypothalamic-pituitary axis causing blunted TSH, GH, and FSH/LH responses to TRH, GHRH, and GnRH stimulation, respectively. Suppressed GH release has been reported, probably caused by reduced synthesis of GHRH, inhibition of GHRH release or reduced somatotrope responsiveness. Higher levels of PRL in lead intoxication have been reported. In short-term lead-exposed individuals, high LH and FSH levels are usually associated to normal testosterone concentrations, whereas in long-term exposed individuals' low testosterone levels do not induce high LH and FSH concentrations. These findings suggest that lead initially causes some subclinical testicular damage, followed by hypothalamic or pituitary disturbance when longer periods of exposure take place. Similarly, lead accumulates in granulosa cells of the ovary, causing delays in growth and pubertal development and reduced fertility in females. In the parenchyma of adrenals histological and cytological changes are demonstrated, causing changes in plasma basal and stress-mediated corticosterone concentrations and reduced cytosolic and nuclear glucocorticoid receptor binding. Thyroid hormone kinetics are also affected. Central defect of the thyroid axis or an alteration in T4 metabolism or binding to proteins may be involved in derangements in thyroid hormone action. Lead toxicity involves alterations on calcitropic hormones' homeostasis, which increase the risk of skeletal disorders.

Exposure to urban stressor and effects on free testosterone in female workers

BACKGROUND

The aim of the study is to evaluate if occupational exposure to chemical, physical and psycho-social urban stressor could cause alterations in plasma free testosterone (T) levels and related diseases in female traffic police vs. control group.

PATIENTS AND METHODS

The research was carried out on initial sample of 468 female Municipal Police employees (209 traffic police and 259 controls). After excluding the principal confounding factors, traffic police were matched with controls by age, working life, menstrual cycle day, BMI, drinking habit, cigarette smoking habit, liquorice and soy intake in diet, habitual consumption of Italian coffee. There were 96 female traffic police and 96 controls included in the study.

RESULTS

T mean levels were significantly higher in female traffic police compared to controls (p=0.000). The distribution of T values in traffic police and in controls was significant (p=0.000). No significant differences were found comparing the percentage in traffic police and controls concerning dystocial, premature and post-term birth. An increase in mental health disorders was found in traffic police compared to controls but the difference was not significant.

CONCLUSION

The increase in T plasma levels observed in traffic police vs. controls can be due to a chronic working exposure to low doses of environmental chemical urban stressor. According to our previous researches T could be used as an early biological marker even before the onset of the related disorders.

Exposure to heavy metals (lead, cadmium and mercury) and its effect on the outcome of in-vitro fertilization treatment

We investigated the effect of lead, cadmium and mercury exposure on pregnancy and fertilization rate outcome among 619 Saudi women (age 19-50 years) who sought in-vitro fertilization (IVF) treatment between 2002 and 2003. The concentrations of lead, cadmium and mercury were measured in both blood and follicular fluids. At levels well below the current US occupational exposure limit guidelines (40microg/dL) and even less than the current Centers for Disease Control and Prevention level of concern for preventing lead poisoning in children (10microg/dL), blood lead level was negatively associated with fertilization outcome in both adjusted and unadjusted logistic regression models. We found that among various demographic, socioeconomic and environmental factors, fish consumption was positively associated with blood lead levels. These results support the hypothesis that a raised blood lead level affects infertility and intervention to reduce the lead exposure might be needed for women of reproductive age. The present results also revealed unexpected finding - the positive relationship between follicular cadmium levels and fertilization outcome, which points to the necessity for further investigation. Though adverse effect of mercury on pregnancy outcome or fertilization rate was not evident in this study, mercury5.8microg/L (EPA safety limit) was found in the blood and follicular fluid of 18.7% and 8.3% of the women, respectively. Concerns about its possible adverse effects on the physiology of reproduction or fetal development cannot be ruled out. It should be noted that skin-lightening creams and dental amalgam were important contributors to mercury exposure. Such finding is alarming and priority for further studies are, urgently, needed.

The relationships between blood lead levels and serum follicle stimulating hormone and luteinizing hormone in the third National Health and Nutrition Examination Survey

The relationships between blood lead levels and serum follicle stimulating hormone and luteinizing hormone were assessed in a nationally representative sample of women, 35-60 years old, from the third National Health and Nutrition Examination Survey. The blood lead levels of the women ranged from 0.7 to 31.1 microg/dl. The estimated geometric mean was 2.2 microg/dl, and the estimated arithmetic mean was 2.8 microg/dl. As the blood lead level increased across women, the concentration of serum follicle stimulating hormone increased in post-menopausal women, women who had both ovaries removed, and pre-menopausal women. The concentration of follicle stimulating hormone decreased in pre-menopausal women who were taking birth control pills. The concentration of luteinizing hormone increased as blood lead level increased in post-menopausal women and women who had both ovaries removed. The lowest concentrations of blood lead at which a relationship was detected were 1.7 microg/dl for follicle stimulating hormone and 2.8 microg/dl for luteinizing hormone. The increase in follicle stimulating hormone and luteinizing hormone in women with no ovaries indicates that lead may act at a non-ovarian site in the female reproductive system, along with a possible effect on the ovaries.

Simultaneous effect of lead and cadmium on granulosa cells: a cellular model for ovarian toxicity

Lead (Pb) and cadmium (Cd) are known reproductive toxicants, which accumulate in granulosa cells of the ovary. Female Charles foster rats were treated with sodium acetate (control), lead acetate and cadmium acetate either alone or in combination at a dose 0.05 mg/kg body weight intra-peritoneally for 15 days daily. Animals were killed at proestrous stage and granulosa cells were isolated from the ovaries. Binding of (125)I-luteinizing hormone ((125)I-LH), (125)I-follicle stimulating hormone ((125)I-FSH) and 17beta-hydroxysteroid dehydrogenase activity were measured. As these receptors are localized on the surface of the cell membrane, we also estimated the membrane parameters of these cells. Our results demonstrated that both lead and cadmium caused a significant reduction in gonadotropin binding, which altered steroidogenic enzyme activity of granulosa cells. These changes exhibited a positive correlation with membrane changes of the granulosa cells.

Damage to ovarian development and function

Ovarian function in women can be compromised by exposure to toxic environmental factors. Chemicals that affect ovarian function can act through direct effects on hormone action (ovary) or by interference with steroid hormone action (hypothalamus and/or pituitary). These effects can cause problems in the form of infertility. Alternatively, ovarian toxicants can directly cause ovarian failure by extensive follicular destruction. This targeting can result in loss of ovarian steroid hormones, eventual ovarian failure (menopause), and ultimate disruption of neuroendocrine feedback causing increased levels of FSH and LH. This article provides an overview of chemicals that in animal studies have been identified to cause disrupted ovarian function with a focus on the sites of targeting by which these disruptions occur. In predicting the impact of environmental factors on reproductive function in women, it is critical to gain a better appreciation of the physiological consequences resulting from the potential variety of mechanisms by which toxicants can disrupt ovarian function. This article attempts to provide such a perspective within the context of specific chemicals for which ovarian sites of toxicity have been identified.

Lead reduces messenger RNA and protein levels of cytochrome p450 aromatase and estrogen receptor beta in human ovarian granulosa cells

Exposure to lead causes decreased fertility in women. In the present study, we examined the in vitro effects of lead on cytochrome p450 aromatase (p450 arom) and on estrogen receptor beta (ERbeta), two key proteins for the human ovary. Aromatase is required for the bioconversion of androgen to estradiol; ERbeta mediates estrogen effects in granulosa cells. Granulosa cells were collected from women undergoing in vitro fertilization and then cultured with 10 microM lead acetate. Using atomic absorption spectrometry, we showed that lead accumulated in cells. Aromatase activity as measured by a tritiated water production assay was significantly reduced. Using semiquantitative reverse transcription-polymerase chain reaction and Western blotting procedures, we showed that p450 arom and ERbeta mRNA and protein content were both significantly reduced. Adding 10 microg/ml of cycloheximide, a protein inhibitor, did not eliminate the effects of lead. The present results support the hypothesis that the action of lead on fertility in women may result, in part, from the down-regulation of p450 arom and ERbeta gene transcription in ovarian granulosa.

Lifetime socioeconomic position in relation to onset of perimenopause

STUDY OBJECTIVE

To assess the association between lifetime socioeconomic position and onset of perimenopause.

DESIGN

Prospective cohort study.

SETTING

Boston, Massachusetts.

PARTICIPANTS

603 premenopausal women aged 36-45 years at baseline who completed a cross sectional survey on childhood and adult socioeconomic position.

MAIN OUTCOME MEASURES

Time to perimenopause, defined as time in months from baseline interview to a woman's report of (1) an absolute change of at least seven days in menstrual cycle length from baseline or subjective report of menstrual irregularity; (2) a change in menstrual flow amount or duration; or (3) cessation of periods for at least three months, whichever came first.

MAIN RESULTS

Incidence of perimenopause was 1.75 times higher (95%CI 1.10 to 2.79) and median age at onset was 1.2 years younger (44.7 v 45.9 years) for women reporting childhood and adult economic distress compared with women reporting no lifetime economic distress. After adjustment for age, race/ethnicity, age at menarche, parity, oral contraceptive use, family history of early menopause, depression, smoking, and body mass index, the association weakened (incidence rate ratio (IRR)=1.59; 95%CI 0.97 to 2.61). Inverse associations were observed for most, but not all, measures of educational level. Measures of current household income were not associated with risk of perimenopause.

CONCLUSIONS

This study suggests that adverse socioeconomic conditions across the lifespan, when measured in terms of economic hardship and low educational attainment, may be associated with an increased rate of entry into perimenopause.

[Cytotoxic effects of lead on the endocrine and exocrine sexual function of pubescent male and female rats. Demonstration of apoptotic activity]

This study deals with the impact of chronic exposure to lead on male and female fertility in rats. Male and female rats (3 months old) were fed on commercial tablets (SICO, Sfax). For drinking, some rats were given distilled water (T = controls), the other ones were given distilled water enriched with lead acetate, either 3 (P1 group) or 6 mg ml-1 (P2 group), for 15, 30, 45, 60 or 90 days. In male rats, absolute and relative weights of testis, epididymis, prostate and seminal vesicles were found to significantly decrease at day 15 in the P2 group and at day 45 in the P1 group. However, at day 60, these absolute and relative weights returned to control values. Lead-induced pathological changes in spermatogenesis were observed at day 15 by histological study: arrest of cell germ maturation, changes in the Sertoli cells, and presence of apoptotic cells revealed by borated toluidine blue in the testis. Presence of lead deposits was observed after histochemical staining using sodium rhodizonate. Serum testosterone level was found to be lowered at day 15 in both (P1) and (P2) groups, to display a peak at day 60, then to return to controls values, in spite of the continuation of the treatment. In female rats, absolute and relative weights of ovary and uterus were found unchanged. The vaginal smears practiced in females revealed the oestrus phase in all groups. Exposed females were mated with control males, and fecundity was assessed 15 days later by counting the number of pregnancies and the number of concepti per pregnancy. Fertility was found to be reduced in females of P1 and P2 groups as compared to control females (T group). Lead level in blood was found to be poorly correlated with the level of poisoning, whereas lead accumulation in tail was found to be dose-dependent. Therefore, lead accumulation in tail appears as a more reliable biomarker of exposure to lead. In summary, our study shows that chronic exposure to lead causes a double sexual disorder in rats: first, disorder deals with the hormonal function, which is affected at the early stages of poisoning, but is rapidly corrected; second, disorder deals with the genital tract, affecting the testis and the ovary, resulting in a reduced fertility in both P1 and P2 females, in spite of the presence of a normal oestrus. The cytotoxic effect of lead in males seems to be related to an apoptotic process.

Lead accumulation in the mouse ovary after treatment-induced follicular atresia

Although the main target of lead (Pb) toxicity is the red blood cell, Pb-associated changes in the nervous system, the kidney, and the reproductive system have also been described. The few Pb studies conducted on females revealed mostly miscarriages, premature delivery, and infant mortality in humans and animals. This study was done to correlate Pb accumulation in the ovary with damage to folliculogenesis. Pb burden was assayed by atomic absorption spectrometry in bone, liver, adrenal glands, ovary, and fetuses taken from mice exposed according to 2 protocols: intraperitoneal (i.p.) injection of Pb(NO(3))(2) 10 mg/kg/day for 15 days or 10 mg/kg/week for 15 weeks. Ovaries were examined histologically. Pb accumulation in the various soft tissues of acutely exposed mice was similar, and significantly higher than in the organs of chronically exposed mice. A low Pb concentration in the ovary caused dysfunction of folliculogenesis, with fewer primordial follicles and an increase in atretic antral follicles.