Journal
GENERAL AND COMPARATIVE ENDOCRINOLOGY
Volume 139, Issue 1, Pages 55-60Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ygcen.2004.07.004
Keywords
thyroxine; 3,5,3 '-triiodothyronine; fathead minnow; development
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The fathead minnow is widely used in ecotoxicological studies and such investigations have begun to focus on potential disruption of the thyroid axis. However, normal levels of thyroxine (T-4) and 3,5,3'-triiodothyronine (T-3) and their developmental patterns are unknown. To provide these baseline data, radioimmunoassays were developed and validated for analysis of T-4 and T-3 after extraction from plasma or whole fish. Female fish showed consistently higher plasma levels of T-4 than male fish. Analysis of thyroid hormones during development showed a significant rise in both T-4 and T-3 during the pre-hatch period, indicating embryonic production of both thyroid hormones. After hatching, whole-body content of both T-4 and T-3 significantly increased in early development, peaking at 16 days post-hatch (dph) and 9 dph, respectively, when T-4 reached 32.88 +/- 3.30 ng g(-1) body weight and T-3 reached 24.17 +/- 3.15 ng g(-1) body weight. Thyroid hormones subsequently declined to a low plateau in later development with approximately 5 ng g(-1) body weight T-4 and 2 ng g(-1) body weight T-3. These data suggest a prominent role for thyroid hormones in early developmental processes when we predict that the ecotoxicological effects of thyroid disrupters will be most significant. (C) 2004 Elsevier Inc. All rights reserved.
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