|MEETING SITE HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX PROGRAM # INDEX ITINERARY SIGNUP|
(HOR-1117-820222) A Xenopus laevis thyroid gland explant culture system for testing chemical disruption of thyroid function.
Hornung, M1, Tietge, J1, Korte, J1, Bugge, M1, Degitz, S1, 1 US Environmental Protection Agency, Duluth, MN, USA
ABSTRACT- Thyroid gland explant culture may be a useful in vitro system for investigating the response of the thyroid gland to stimuli independent of the hypothalamic-pituitary-thyroid (HPT) axis, and may provide a format for testing the potential of chemicals to perturb normal thyroid gland function. Thyroid glands from pro-metamorphic Xenopus laevis tadpoles were dissected and cultured at 20°C in a 96-well plate containing L-15 media with 0.1% bovine serum albumin. To assess their response to thyroid stimulating hormone (TSH), individual glands were cultured for several days in media containing 0, 250, 500, 1000, or 2000 ng bovine TSH/ml. Media was collected at 24h intervals with complete replacement and assayed by ELISA for thyroxine (T4). Paired glands cultured in 0, 500, or 1000 ng TSH/ml were collected at 0, 24, or 48h and assayed by real-time PCR for expression of the following genes involved in production and regulation of T4: sodium-iodide symporter (NIS), thyroid transcription factor 1 (TTF1), thyroid peroxidase (TPO), thyroglobulin (TG), and Types I, II, and III deiodinase. Thyroid glands showed a dose and time-related response to TSH stimulation. Following treatment with 250 ng TSH/ml, glands maintained a steady daily output of 12-20 ng T4/ml/d through six days in culture. At 2000 ng TSH/ml, T4 in the media was 144 ng/ml at 24h and dropped off daily after that to 30 ng T4/ml/d by 6d. Control glands cultured in the absence of TSH did not release T4 into the media. TSH increased expression of mRNA of NIS, TPO, and Type II deiodinase compared to control glands without TSH stimulation. This system shows promise as a tool to isolate the effect of chemicals on the thyroid gland to further understand the mechanisms by which chemicals may disrupt the HPT axis. This abstract does not necessarily reflect EPA policy.
Key words: amphibian, thyroid gland, xenopus , gene expression
Internet Services provided by|
Allen Press, Inc. | 810 E. 10th St. | Lawrence, Kansas 66044 USA
e-mail email@example.com | Web www.allenpress.com
All content is Copyright © 2005 SETAC