Article

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

Department of Epidemiology and Biostatistics, School of Public Health, Nanjing Medical University, Nanjing, China.
Journal of Toxicology and Environmental Health Part A (Impact Factor: 1.83). 02/2008; 71(7):454-63. DOI: 10.1080/15287390701839331
Source: PubMed

ABSTRACT 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.

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    • "In addition, a significant positive correlation was also observed between Pb in seminal plasma and the 8-hydroxy-2'-deoxyguanosine (8-OHdG) level (Xu et al., 2003). Pb is a testicular toxicant in experimental animals (Wang et al., 2008). The effects of Pb on spermatogenesis have been demonstrated in rat testes. "
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    • "In the animal model, lead has a primary toxic effect on the hypothalamic-pituitary unit, a primary effect on the testes and acts at all levels of the reproductive axis (Sokol et al., 2002). Male rats exposed to lead acetate have been reported to show a significant decrease in the weight of both the testes, epididymis (Wang et al., 2008; Smith et al., 2008) and pituitary (Cooper et al., 1986; Coffigny et al., 1994) and this weight reduction in sex glands and pituitary was accompanied by an alteration of the normal histological structure. There are reports that some metal such as lead, cadmium, arsenic and mercury can affect male reproductive functions including sperm counts (Chia et al., 1992), motility and morphology (Meeker et al., 2008) and spermatogenesis (Telisman et al., 2007). "
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