Neuroendocrine Disruption

Compounds that have the property to disrupt the neuroendocrine signaling and the metabolisms of hormones and neuromediators in organisms are termed neuroendocrine disrupters. Previously named endocrine disrupters, the scientific community realized that many neuromediators are also involved in other systems or functions such as growth, food intake (behavior), gonad development, and sexual differentiation. These observations suggested that neural and endocrine signaling, especially those involved in reproduction, were associated or physiologically coupled. Estrogenic compounds capable of acting as estrogen mimics in respect to biochemical targets in cells are by far the most studied type of endocrine disrupters in the wild. Indeed, estrogen binding to receptors leads to important physiological changes, including the mobilization of energy reserves and the production of vitellogenin, the egg-yolk protein precursor in oviparous organisms. Vitellogenin represents the main food source for the developing embryos post hatch. This response could also be obtained in males or in juveniles. Expression of vitellogenin in males was also the first step leading to intersex or male feminization in fish and mussels. Both generic and specific assays to detect for the presence of estrogenic effects and estradiol-17β binding sites in aquatic organisms are presented. The evaluation of catecholamines (dopamine and noradrenaline) and indolamines (serotonin) using less specific (fluorescence assay) and more specific means (competitive immunoassay) is also presented to accommodate various laboratory sizes and budgets. Finally, some enzyme-based assays are also presented for acetylcholine and catecholamine/indolamine turnover studies using prepared nerve button synaptic membranes, which are operationally termed synaptosomes.