Recently, TBECH was shown to be present in beluga whales and herring gull eggs at nanomolar concentrations (Gauthier et al. 2009; Tomy et al. 2008). Low-level exposure to endocrine-disrupting compounds can induce functional, developmental, behavioral, and transgenerational disturbances, as shown after low-level exposure to the fungicide vinclozolin, which acts as an androgen antagonist in rats and mice (Anway et al. 2006, 2008; Elzeinova et al. 2008; Skinner et al. 2008). Therefore, although low-level exposure to the most common TBECH, TBECH-β, may not induce high AR activation, these compounds may nonetheless induce transgenerational effects at the observed levels.
The natural ligands testosterone and DHT showed maximal hAR activation already after 8 hr (Figure 4). A recent study showed that HepG2 cells rapidly metabolized testosterone and DHT, resulting in 82% and 46% reduction, respectively, 21 hr after addition of the hormone (Simon and Mueller 2006). In contrast, determination of time-dependent hAR activation by TBECH indicates slower receptor activation and prolonged induction times, suggesting that these compounds are more stable in this cell line. The stability of TBECH is further supported by the discovery of its presence in the environment (Gauthier et al. 2009; Tomy et al. 2008) as well as its ability to be maternally transferred in zebrafish (Nyholm et al. 2008).
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