Thyroid hormone regulation of ovarian steroidogenesis in the amphibian, Xenopus (Silurana) tropicalis.
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1
University of Prince Edward Island, Biology Department, Canada
Adequate levels of circulating thyroid hormone (TH) are of primary importance for normal steroid hormone production in the vertebrate gonad. In this context, the presence of compounds in the environment that disrupt TH levels may pose a significant threat to the reproductive health of amphibians. This study was conducted to determine the effects of TH on gonadal steroidogenesis in an amphibian model species, Silurana tropicalis. In an in vitro steroidogenesis assay, ovarian tissue from adult females was incubated in the presence or absence of 10 IU hCG and various concentrations of the TH, triiodothyronine (T3; 0.1 nM-1 µM), for 18 hours. Hormone levels (testosterone, T; estradiol, E2) in the incubation media were measured by radioimmunoassay. Treatment with T3 had no effect on T but decreased E2 production in ovarian tissue at the highest T3 concentrations. To determine the potential sites of T3 action within the steroidogenic pathway, mRNA levels of key steroidogenic genes were evaluated using qPCR. There was no effect of treatment on the expression of steroidogenic genes. The results of this study demonstrate that T3 can modulate ovarian steroidogenesis but that this response is not related to transcript-level changes in steroidogenic genes, and could possibly be linked to phosphorylation and activation of transcription factors. Further studies will examine how changes in thyroid status can influence reproduction, responsiveness to other hormones and hormone-active contaminants
Acknowledgements
Research supported by NSERC Discovery Grant to NSH.
Keywords:
cross-regulation,
in vitro,
Ovary,
Radioimmunoassay,
Real-Time PCR,
steroidogenesis,
Thyroid hormone
Conference:
ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology, Ann Arbor, United States, 11 Jul - 13 Jul, 2011.
Presentation Type:
Poster
Topic:
Reproduction
Citation:
Gordon
D,
Allen
A and
Hogan
N
(2011). Thyroid hormone regulation of ovarian steroidogenesis in the amphibian, Xenopus (Silurana) tropicalis..
Front. Endocrinol.
Conference Abstract:
ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology.
doi: 10.3389/conf.fendo.2011.03.00013
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Received:
21 Jul 2011;
Published Online:
09 Aug 2011.
*
Correspondence:
Dr. Natacha Hogan, University of Prince Edward Island, Biology Department, Charlottetown, PE, C1A 4P3, Canada, natacha.hogan@gmail.com