Evidence Of Endocrine Disruption Research Articles

Gender benders at the beach: Endocrine disruption in marine and estuarine organisms

Several consensus definitions of the term endocrine disruptor have appeared recently, but all definitions include the important, though frequently implicit, stipulation that the animal is not distressed or in obvious discomfort. Instead, a superficially healthy animal is experiencing alterations in hormone synthesis, transport, receptor interaction, metabolism, excretion, or feedback regulation. In addition, hormone disruption may occur during sex differentiation, and its effects may not be manifested until after sexual maturation. Many cases of chemically induced reproductive impairment have been reported for both freshwater and marine species. However, reproductive impairment may not necessarily result from hormone disruption and should be considered suggestive, but not conclusive, evidence of endocrine disruption. A suite of in vivo and in vitro assays will more adequately assess whether a compound is truly endocrine disrupting. This review will cover basic endocrinology of marine and estuarine invertebrates and vertebrates, methods for detecting endocrine disruption, and examples of endocrine disruption in various species.

Mechanisms of Endocrine Disruption with Particular Reference to Occurrence in Avian Wildlife: A Review

This review examines the evidence for endocrine disruption in birds. It reviews in vitro and in vivo laboratory based evidence for endocrine disruption by (1) agonism or antagonism of gonadal steroid hormones, (2) altering the activity of cytochrome P450 enzymes, (3) altering thyroid hormone function, (4) affecting intrinsic neuroendocrine control mechanisms and (5) activation of the stress response. It also discusses the evidence for the existence of such effects in free-living birds. In vitro studies demonstrate that mechanisms for potential endocrine disruption exist, but in vivo studies suggest that such mechanisms are insufficient to overwhelm endogenous homeostatic control. There are only two phenomena in wild birds where endocrine disruption has been cited as a possible cause: eggshell thinning and supernormal clutches. Evidence suggests that neither of these is caused by endocrine disruption. Despite three decades of concern, there is no evidence that avian wildlife has suffered endocrine disruption.

Evidence of endocrine disruption in clams — Ruditapes decussata — transplanted to a tributyltin-polluted environment

Clams— Ruditapes decussata— were transplanted to an organotin-polluted marina for a period up to 5 weeks. Tributyltin (TBT) was the major organotin compound detected in clams; TBT accumulation was extremely rapid, it reached a maximum tissue concentration of 290 ng/g wet weight 3 weeks after transplant, which represents a bioaccumulation factor of 12,000. Dibutyltin, monobutyltin and triphenyltin were also detected, although at a lesser extent (4–22 ng/g wet wt). Investigations on endogenous steroid content by radioimmunoassay revealed important changes in TBT-exposed clams. A 33% increase in testosterone titres was observed 5 weeks after transplant. Likewise, a time-dependent decrease in oestradiol levels was evidenced, viz. oestradiol titres decreased 2, 3.5 and 5-fold in clams sampled 1, 3 and 5 weeks after transplant, respectively. These observations together with previous data on TBT-exposure experiments suggest a potential masculinization of clam physiology as a consequence of TBT exposure.

Evidence of Endocrine Disruption in the Imposex-Affected Gastropod Bolinus brandaris

Testosterone/estradiol tissue levels and cytochrome P450-dependent aromatase activity have been evaluated in the gastropod Bolinus brandaris. Samples were collected from two locations on the Mediterranean coast (St. Carles and Barcelona) according to their different degrees of imposex development and organotin residues. St. Carles was chosen as a relatively clean site, as only 37% of the females were imposex affected compared to 100% of the females from Barcelona. A strong reduction of estradiol levels was seen in both males and females from the organotin-polluted site in comparison to those of the reference site, whereas weaker differences between the sites in testosterone levels were revealed. Despite the observed alterations in sex hormone levels, no changes in aromatase activity were recorded. These results suggest that mechanisms other than inhibition of aromatase activity might be involved in the development of imposex in B. brandaris.

Inhibition of barnacle settlement by the environmental oestrogen 4-nonylphenol and the natural oestrogen 17β oestradiol

The present study examines the effect of a known environmental oestrogen, 4-nonylphenol, on the settlement of the cypris larva of the barnacle, Balanus amphitrite. Cypris larvae were exposed to 4-nonylphenol in a nominal concentration range of 0.01–10.0 μg l −1. Definitive concentrations of 4-nonylphenol in the test solutions were determined by GC/MS. Cyprid settlement was reduced significantly within this concentration range, following incubation at both 25°C and 28°C for 24–48 h. A naturally occurring oestrogen, 17β oestradiol, was used as a positive control, in the concentration range 0.01–10.0 μg l −1. Larval settlement was inhibited by 17β oestradiol, but the trend was the opposite to that seen with 4-nonylphenol. No evidence of endocrine disruption was demonstrated, but significant inhibition of larval settlement by both 4-nonylphenol and 17β oestradiol indicated that the compounds may have toxic effects at environmentally realistic and naturally occurring concentrations. The potential for endocrine disruption being more significant at different developmental stages in barnacles is discussed.