Michael F. O’Dea
Amy M. Moeckel
Darrren T. Lerner
Bjorn Thrandur Bjornsson
Stephen D. McCormick
2005
<p><span>Sex </span><a class="linkText">steroids</a><span> are known to interfere with the parr-smolt transformation of anadromous salmonids, and environmental estrogens such as nonylphenol have recently been implicated in reduced returns of </span><a class="linkText">Atlantic salmon</a><span> in the wild. To determine the </span><a class="linkText">endocrine</a><span> pathways by which estrogenic compounds affect smolt development and seawater tolerance, groups of juvenile Atlantic salmon were injected with one of five doses (0.5, 2, 10, 40 or 150 μg g</span><sup>−1</sup><span>) of branched 4-nonylphenol (NP), 2 μg g</span><sup>−1</sup><span> of 17β-</span><a class="linkText">estradiol</a><span> (E</span><sub>2</sub><span>), or vehicle, during the parr-smolt transformation in April, and the treatment was repeated 4, 8, and 11 days after the first injection. Plasma was obtained for biochemical analysis 7 and 14 days after initiation of treatment. After 14 days of treatment, additional fish from each treatment group were exposed to seawater for 24 h to assess salinity tolerance. The E</span><sub>2</sub><span> treatment and the highest NP dose resulted in lower salinity tolerance and decreased plasma insulin-like growth factor I (IGF-I) levels, along with elevated levels of plasma vitellogenin and total calcium. Plasma </span><a class="linkText">growth hormone</a><span> levels were elevated at intermediate NP doses only, and not affected by E</span><sub>2</sub><span>. After 7 days, plasma thyroxine (T</span><sub>4</sub><span>) levels decreased in a strong, dose-dependent manner in response to nonylphenol, but after 14 days, this suppressive effect of T</span><sub>4</sub><span> occurred at the highest NP dose only. Similarly, E</span><sub>2</sub><span> decreased plasma T</span><sub>4</sub><span> levels at 7, but not 14 days. Plasma 3,3′,5-triodo-</span><span class="smallcaps">l</span><span>-thyronine was reduced by E</span><sub>2</sub><span> and the highest NP dose after 7 and 14 days of treatment. Plasma</span><a class="linkText">cortisol</a><span> levels were not affected by any of the treatments. The results indicate that the parr-smolt transformation and salinity tolerance can be compromised by exposure to estrogenic compounds. Suppression of plasma IGF-I levels is a likely endocrine pathway for the effects of estrogenic compounds on hypo-osmoregulatory capacity, and the detrimental effects of E</span><sub>2</sub><span> and NP on </span><a class="linkText">thyroid hormone</a><span> levels are also likely to compromise the normal parr-smolt transformation of Atlantic salmon.</span></p>
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10.1016/j.ygcen.2005.01.015
en
Elsevier
Endocrine disruption of parr-smolt transformation and seawater tolerance of Atlantic salmon by 4-nonylphenol and 17β-estradiol
article