Lead induced ultrastructural changes in the testis of rats

Effects of lead exposure on sperm concentrations and testes weight in male rats: a meta-regression analysis

The correlation between exposure to lead (PB) and sperm concentrations and testes weight are important in risk assessment of metal toxicity to male reproductive functions. The authors carried out two systematic reviews and meta-analyses of rats. In addition, a meta-regression analysis was taken to explore a dose-response relationship between the mean difference of testes weight (MD(testes)) and available confounding factors. Data were obtained from computerized literature searches of several databases from their inception through December 2005. The reference lists of identified articles were examined further for relevant articles. The authors identified 6 and 12 studies, separated into 16 and 28 subgroups, in the two meta-analyses. The authors conducted random- or fixed-effect models toward the effect size. Heterogeneity between study results was explored through chi-square tests and meta-regression. Results showed that a decrease in sperm concentrations was found as low as mean difference of sperm concentrations (MD(sperm)) = 30.9 and 95%CI = (25.43-36.37) in a fixed-effect model or MD(sperm) = 35.47 and 95%CI = (15.27-55.68) in a random-effect model after Pb exposure. Similarly, a significantly lower testes weight was also evident: MD(testes) = 0.033 and 95%CI = (0.021-0.046) in a fixed-effect model or MD(testes) = 0.047 and 95%CI = (0.0044-0.089) in a random-effect model. In the meta-regression analysis, two confounders, age and body weight, explained part of the observed heterogeneity. The body weight after Pb exposure was inversely associated with MD(testes). These findings support the notion that Pb exposure produced decreased sperm concentrations and testes weight in rats.

Reproductive potential of male Portan rats exposed to various levels of lead with regard to zinc status

The present study was designed to elucidate the mechanisms accounting for disruption of the normal function of the testis exposed to various levels of Pb. Three different doses of Pb (10, 50, 200mg Pb/kg body weight per d) were given orally to male Portan rats (groups 2, 3, 4). Zn (1mg Zn/kg body weight per d) was also given with Pb (50mg Pb/kg body weight per d) in group 5. Treatments continued for 3 months. Plasma luteinizing hormone and follicle-stimulating hormone concentrations were found to be decreased in Pb-exposed rats. This was in turn reflected in the appreciable decline in fertility status. In cell kinetic studies, significant declines in various cell populations (preleptotene, pachytene, young (step 7) spermatids and mature (step 19) spermatids) were seen. However, in group 5 after Zn supplementation, hormone levels, cell numbers and fertility status were found to be close to normal. It is concluded that Pb might act at maturation level to cause conspicuous degenerative changes in the testis; Zn supplementation protected against these effects.

Occupational exposure and effects on the male reproductive system

A significant increase in the incidence of male infertility has been described in the international literature, raising questions about its causes. Part of this effect may result from synthetic toxic substances acting on the endocrine system (endocrine disruptors), many of which are routinely used in work processes. We provide a critical review of the specialized literature on work-related chemical substances capable of causing male infertility. Pesticides such as DDT, linuron, and others, heavy metals like mercury, lead, cadmium, and copper, and substances from various industrial uses and residues such as dioxins, polychlorinated biphenyls (PCBs), ethylene dibromide (EDB), phthalates, polyvinyl chloride (PVC), and ethanol are among the main endocrine disruptors that can cause male infertility. Based on the literature, gonadal dysfunction and congenital malformation are the main alterations caused by these substances in the male reproductive system. We conclude that despite the relative lack of studies on this issue, the relevance of such risk calls for further studies as well as measures to prevent workers' exposure to the various substances.

Detection of lead-induced oxidative stress in the rat epididymis by chemiluminescence

It has been shown that lead (Pb) is able to induce lipid peroxidation, one of the main manifestations of oxidative stress. In this study we examined the relationship between chronic Pb exposure and level of reactive oxygen species (ROS) in reproductive system tissues of sexually mature male Wistar rats. One group of animals (control, K) was allowed to drink distilled water, the second group (Pb) was allowed to drink freely 1% aqueous solution of lead acetate. Another groups had a following supplements: rats were allowed to drink distilled water containing vitamin C (vit C) at concentration of 500 mg/l or Trolox (a vitamin E analog) at concentration of 48 mg/l or vit C (500 mg/l) + Trolox (48 mg/l). The similar groups among Pb-treated animals were examined after treatment with the same vitamins and using the same vitamin doses, dissolved in 1% aqueous solution of lead acetate. In all cases the time of drinking was 6 months. It was found that lead content in samples of tissues from testis, epididymis and in a whole blood in Pb- and Pb with antioxidants treated rats was significantly elevated. Chemiluminescence (CL) emitted by the Pb-treated tissues was significantly higher when compared to the light emission by tissues isolated from the animals of control group. The increase in the CL caused by lead occurs in the following increasing order within the studied tissues: cauda of epididymis < testis < caput of epididymis (19%, 39% and 51%, respectively). Dietary vit C supplementation to the Pb-treated rats for 6 months period decreased the CL from caput of epididymis, cauda of epididymis and testis (by 43%, 24%, 39%, respectively) more effectively in comparison to the control group (35%, 17%, 33%, respectively). Also stronger quenching effect on the light emission from the above mentioned tissues after Trolox supplementation was observed in the Pb-treated group (42%, 21%, 35%, respectively) than in the control group (23%, 13%, 13% respectively). The combination of both antioxidants treatments (vit C and Trolox) did not give a higher significant quenching effect compared to the treatment with the vitamins separately. No ultrastructural changes were found in the seminiferous epithelium of Pb-treated animals. However, we found abnormalities in ultrastructure of epididymal epithelial cells and epididymal spermatozoa in rats of Pb-treated groups. These findings provide ex vivo evidence that Pb causes oxidative cellular damage in reproductive system tissues of adult male rats, which may be closely associated with the ROS production.

Lead intoxication in gestational and lactation periods alters the development of male reproductive organs

The effect of lead (Pb) intoxication during pregnancy and lactation on the male reproductive system was studied to evaluate the alterations caused by Pb in the development of pups. The investigations covered the effect of lead on the course of spermatogenesis and the development of the epididymis and reproductive glands. For this purpose, dams were intoxicated with 300 mg/L Pb during the gestational period and through lactation. Pups were sacrificed on Postnatal (PN) Days 12 and 21. Blood lead (PbB) and plasma iron concentrations were measured, and blood cells counted. Biochemical studies as well as histochemical analyses were performed on testes and accessory glands of the reproductive system. Lead intoxication resulted in a decrease in testis and seminal vesicle weights and an increase in DNA and RNA levels on PN Day 21. Total protein was significantly decreased by the toxicant, and alkaline and acid phosphatase levels of the gonads were reduced. Effects were also reflected in the reduction of the thickness of epithelium and of seminiferous tubule diameter (STD) as a consequence of the action of lead in the reduction in numbers of prospermatogonia and spermatocytes. Results indicate that the reproductive system targets of lead intoxication are not only the testes; lead intoxication results in the inhibition of testicular, epididymal, and seminal vesicle function, altering the biochemical composition of these organs, and consequently, affecting the normal development of germinal cells.

Influence of lead and zinc on rat male reproduction at 'biochemical and histopathological levels'

Sequential lead accumulation and biochemical and histopathological changes were observed in rat testis and epididymis after oral administration at varied doses of lead (10, 50 and 200 mg kg(-1) body wt.) for 3 months and also following the concomitant administration of lead with zinc (1 mg kg(-1) body wt. +50 mg Pb kg(-1) body wt.). Accumulation of lead in both testis and epididymis increased with dose. The concomitant administration of zinc reduced the lead levels. Similarly, dose-related changes were seen in the activities of the enzymes alkaline phosphatase and Na(+)-K(+)-ATPase, which decreased with increased dose of lead. A significant improvement in the activities of these enzymes was seen in the groups given both lead and zinc. Histologically, discernible changes were noticed only at higher doses (50 and 200 mg kg(-1) body wt.), which included disorganization and disruption of spermatogenesis with accumulation of immature cells in lumen of tubule. At higher doses of lead, complete arrest of spermatogenesis was seen and a significant decrease in germ cell layer population was evident. Even in epididymis, the histoarchitecture was disrupted only at higher doses of lead both in the caput and corpus regions. The changes included damage of basement membrane, disorganization of epithelium and vacuolization of cells. The tubules were found almost empty, indicating arrest of spermatogenesis. However, with concomitant administration of lead and zinc both testis and epididymis presented a near-normal picture, indicating the protective role of zinc. Hence, the data indicate that the protective effect of zinc on lead toxicity was mediated largely by significant competition between lead and zinc or due to reduction of the available binding sites.

Effect of lead on Sertoli-germ cell coculture of rat

Mixed cultures of Sertoli and germ cells were prepared from rat testes and their response to lead (Pb) was studied. Cultures consisted of a monolayer of Sertoli cells to which clusters of germ cells were attached. The effect of Pb added as lead acetate was tested at 0.0, 0.4, 4.0 and 40.0 microM for 24 and 48 h intervals. Addition of Pb to the culture medium caused germ cells to progressively detach from the Sertoli cell monolayer into the medium in a concentration and duration dependent manner Viability of the detached cells as judged by trypan blue exclusion test showed a decrease with increase in time and concentration of Pb. Significant leakage of lactate dehydrogenase (LDH) was recorded in the culture media only at the higher concentrations of 4.0 and 40.0 microM. Thus Pb at the doses tested induced cytotoxicity in rat Sertoli-germ cell coculture.

Male reproductive toxicity of lead in animals and humans. ASCLEPIOS Study Group

OBJECTIVE

To critically review the literature on male reproductive toxicity of lead in animals and humans.

METHODS

A systematic literature search identified a total of 32 experimental studies in animals and 22 epidemiological studies, one case report on humans and five review articles or documents. The studies were evaluated by paying attention mainly to sample size, study design, exposure, and dose characterisation, analytical method standardisation, and quality assurance.

RESULTS

Several studies on rats and other rodents indicated that blood lead concentrations > 30-40 micrograms/dl were associated with impairment of spermatogenesis and reduced concentrations of androgens. However, other animal studies, mainly about histopathological, spermatozoal, and hormonal end points, indicated that certain species and strains were quite resistant to the reproductive toxicity of lead and that different testicular lead concentrations could account for these differences. The human studies focused mainly on semen quality, endocrine function, and birth rates in occupationally exposed subjects, and showed that exposure to concentrations of inorganic lead > 40 micrograms/dl in blood impaired male reproductive function by reducing sperm count, volume, and density, or changing sperm motility and morphology. No relevant effects were detected on endocrine profile.

CONCLUSION

Several factors make it difficult to extrapolate the animal data to the human situation. The difficulties are mainly due to differences between species in reproductive end points and to the level of exposure. Concentrations of blood lead > 40 micrograms/dl seemed to be associated with a decrease in sperm count, volume, motility, and morphological alterations and a possible modest effect on endocrine profile. Dose-response relation, in particular at a threshold level, is poorly understood, and site, mode, or mechanism of action are unknown. Also, the effects were not always the same or associated in the same on sperm count and concentration. Some methodological issues and indications for future studies are discussed.

Chronic lead exposure effects in the cynomolgus monkey (Macaca fascicularis) testis

Although reproductive consequences of high circulating blood lead levels (> or = 60 micrograms/dL) have been reported, potential adverse effects of chronic lead exposure in males that result in low to moderate blood lead levels (10-25 and 26-60 micrograms/dL, respectively) are unknown. Effects of chronic lead exposure to testis ultrastructure were determined in the cynomolgus monkey after oral administration of lead acetate (1500 micrograms/kg BW/day) in a vehicle in the following groups: from birth to 10 years (lifetime), postnatal day 300 to 10 years (postinfancy), and postnatal day 0-400 (infancy); monkeys in the control group received only the vehicle (95% glycerol and 5% distilled water). At age 10 years, circulating lead concentrations in lifetime and postinfancy-dosed monkeys were approximately 35 micrograms/dL, and in control and infancy animals the concentrations were < 1.0 microgram/dL. Sertoli and spermatogenic cells of dosed monkeys from the infancy and lifetime groups revealed injuries. Chronic exposure to lead that results in moderate blood lead concentrations induced persistent ultrastructural alterations in the cynomolgus monkey testis. Results of this study on the primate, following extrapolation to humans, could influence further refining of the impact of environmental lead contamination concentrations vis-à-vis the health of children, adults, and aged human beings.

Suramin-induced ultrastructural changes in the testis of albino rats

The effect of chronic suramin administration on rat testis was evaluated. The animals were given the drug twice a week for two months, following a treatment schedule comparable to that used in cancer therapy. Light microscopic sections revealed vacuolizations near the basal lamina, germ cells very little differentiated, together with immature cells located in the lumen of seminiferous tubules. Ultrastructural changes were revealed in the form of a decrease in nuclear density with evaginations of the nuclear envelope and sometimes ruptures of the plasmatic membrane. Changes in the Sertoli cells consisted of cytoplasm vacuolizations, in which some lysosomes, containing degraded material such as myelin-like figures, were present.

The ultrastructure of the testis in rats after long-term treatment with lead acetate

Studies were performed to investigate the influence of long-term lead acetate treatment on morphology of rat testis. No marked changes were observed by means of light microscopy. At all stages (I-XIV) of the seminiferous epithelium cycle, all generations and layers of spermatogenic cells were present. Electron-microscopic studies did not reveal any ultrastructural changes neither in seminiferous epithelium nor in Sertoli cells. In Leydig cells also, no ultra-structural abnormalities were visible. Macrophages of testicular interstitial tissue contained electron-dense inclusions, usually located inside phagolisosome-like vacuoles. X-ray micro-analysis revealed that the inclusions contained lead.

Reproductive endocrine effects of chronic lead exposure in the male cynomolgus monkey

The reproductive endocrine effects of chronic lead exposure were investigated in 9 year old male (n = 16) cynomolgus monkeys, orally dosed with lead acetate (1500 micrograms/kg/day) according to the following dosing regimens: continuous exposure from birth onward (lifetime, n = 4), beginning at postnatal day 300 (post-infancy, n = 5) and postnatal days 0 to 400 (infancy, n = 4), or vehicle only (control, n = 3). Altered Sertoli cell function was shown by a significant (P = 0.0286) decrease in the inhibin/follicle stimulating hormone (INH/FSH) ratio in both the lifetime and post-infancy groups compared to the control group. Gonadotropin releasing hormone (GnRH) stimulated levels of luteinizing hormone (LH) were significantly (P = 0.0370) lower in the lifetime group compared to the control group as determined by comparisons of the area under the curve. These data suggest that chronic lead exposure exerts a subtle effect on the pituitary as well as on Sertoli cell function.