Chemicals that mimic natural oestrogens have well-documented effects on the reproductive systems of vertebrates, typically acting as endocrine disruptors, but scientists know much less about how these chemicals affect other tissues and body systems. Researchers have explored zebrafish transgenically modified to glow with green fluorescent protein (GFP) as a way to detect effects of different oestrogenic chemicals in real time. A British team now confirms and improves upon previous work by developing an even more sensitive transgenic zebrafish biosensor for assessing potential endocrine disruptors. Earlier transgenic models reported exposure only in certain tissues or at very high doses. In the current study, the researchers exposed embryonic transgenic zebrafish at 1 hour post fertilisation to environmentally relevant doses of five different oestrogenic chemicals: the plasticiser bisphenol A (BPA), the industrial surfactant 4-nonyl-phenol (NP), the natural steroids oestrogen and 17?-oestradiol (E2), and 17?-ethinylestradiol (EE2), a synthetic hormone widely used in contraceptive pills and hormone replacement therapy. A new transgenic zebrafish model offers a more sensitive method for studying responses to environmentally relevant doses of oestrogenic chemicals. Tissues such as the liver, forebrain, lateral line (a sensory system found in aquatic vertebrates), otic vesicles, eyes, heart, and cranial and somite muscle appeared to be strongly affected by some of the compounds tested, but not others. In addition, the study found that different tissues response to EE2 was time dependent. For example, liver, heart, and muscle tissue began to glow 24 hours post fertilisation and reached maximum strength at 96 hours, whereas a significant increase in fluorescence was seen in the otic vesicles 48 hours post fertilisation, and in the eyes and forebrain after 72 hours. Based on this study, the zebrafish biosensor seems a promising and powerful system to test the impacts of a variety of oestrogenic chemicals in a living vertebrate at low, environmentally relevant doses. The authors suggest the system could be developed for high-throughput screening, an urgent need in the study of endocrine-disrupting chemicals.
Environmental Health Perspectives, 2 July 2012 ;http://ehp03.niehs.nih.gov ;