US researchers have evidence that damage to mammalian male fertility caused by transient exposure of embryos to endocrine-disrupting environmental toxins can be passed down to subsequent generations.1 "The endocrine disruptors appear to have altered the remethylation and permanently reprogrammed the germ line, that is, sperm," explains study coauthor Michael Skinner of Washington State University in Pullman.

Skinner and colleagues exposed female rats in mid gestation to high doses of two endocrine disruptors, the anti-androgenic vinclozolin and the estrogenic methoxychlor. More than 90% of male offspring had low sperm counts and abnormal sperm production, with 10% being completely infertile. An almost identical pattern of male fertility impairment was passed down to second-, third-, and fourth-generation males whose parents were not exposed to the toxins. The culprit appears to be DNA remethylation that occurs at the time of gonadal sex determination shaping the patterns of gene expression in the offspring.


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