Propylthiouracil-induced hypothyroidism in coho salmon, Oncorhynchus kisutch : Effects on plasma total thyroxine, total triiodothyronine, free thyroxine, and growth hormone
(1998) In Fish Physiology and Biochemistry 19(4). p.305-313- Abstract
Thyroid hormones transiently increase during parr-smolt transformation in coho salmon, Oncorhynchus kisutch, and are believed to trigger morphological, physiological, behavioural, and neural changes. The effectiveness of propylthiouracil (PTU) to induce hypothyroidism in smolting coho salmon was determined by immersing coho salmon, Oncorhynchus kisutch, in 30 mg 1-1 PTU from May 1, two weeks prior to the consistent annual total thyroxine (TT4) peak in mid-May, until the last sampling date. Plasma was obtained at two sampling dates from control and PTU -treated coho salmon: May 15, during the plasma TT4 peak; and May 26, after the TT4 peak. Radioimmunoassays were used to measure plasma... (More)
Thyroid hormones transiently increase during parr-smolt transformation in coho salmon, Oncorhynchus kisutch, and are believed to trigger morphological, physiological, behavioural, and neural changes. The effectiveness of propylthiouracil (PTU) to induce hypothyroidism in smolting coho salmon was determined by immersing coho salmon, Oncorhynchus kisutch, in 30 mg 1-1 PTU from May 1, two weeks prior to the consistent annual total thyroxine (TT4) peak in mid-May, until the last sampling date. Plasma was obtained at two sampling dates from control and PTU -treated coho salmon: May 15, during the plasma TT4 peak; and May 26, after the TT4 peak. Radioimmunoassays were used to measure plasma TT4, total triiodothyronine (TT3), free thyroxine (FT4), and salmon growth hormone (sGH). The PTU -treatment inhibited the natural smoltification-related increases in plasma TT4, TT3 and GH levels compared with controls, but PTU-treatment did not affect these hormone levels when they were low. PTU -treatment increased FT4 and decreased TT3 and sGH levels in the May 26 sample. In the May 15 sample, FT4 levels were unaffected by PTU-treatment, whereas TT4 levels were decreased. These data demonstrate the ability of PTU to induce hypothyroidism in salmonids as shown by the decrease in TT4 and TT3. These data demonstrate that PTU treatment by immersion can induce hypothyroidism in salmonids as shown by: (1) the inhibition of the natural increases of TT4 and TT3; (2) the increase in FT4 levels corresponding to the lowered TT3 levels, suggesting an inhibition of thyroxine 5′-monodeiodinase activity. We also show for the first time that PTU treatment can lower plasma GH levels in salmonids. This lowering of plasma GH level is associated with the decrease in TT3 levels and the increase in FT4 levels. Lhe PLU induced lowering in GH levels may contribute to the observed changes in FT4 and TT3, since GH is known to increase thyroxine 5′-monodeiodinase activity.
(Less)
- author
- Ebbesson, L. O.E. LU ; Björnsson, B. Th ; Stefansson, S. O. and Ekström, P. LU
- organization
- publishing date
- 1998-12-01
- type
- Contribution to journal
- publication status
- published
- keywords
- Development, Equilibrium dialysis, Fish, Hypothyroid, Immersion, Radioimmunoassay, Smoltification, Teleost, Thyroid hormones
- in
- Fish Physiology and Biochemistry
- volume
- 19
- issue
- 4
- pages
- 9 pages
- publisher
- Springer
- external identifiers
-
- scopus:0000589893
- ISSN
- 0920-1742
- language
- English
- LU publication?
- yes
- id
- 47b4066e-bfdf-4a59-a4d5-b488e1a96b01
- date added to LUP
- 2019-10-02 14:45:56
- date last changed
- 2022-02-01 01:12:53
@article{47b4066e-bfdf-4a59-a4d5-b488e1a96b01,
abstract = {{<p>Thyroid hormones transiently increase during parr-smolt transformation in coho salmon, Oncorhynchus kisutch, and are believed to trigger morphological, physiological, behavioural, and neural changes. The effectiveness of propylthiouracil (PTU) to induce hypothyroidism in smolting coho salmon was determined by immersing coho salmon, Oncorhynchus kisutch, in 30 mg 1<sup>-1</sup> PTU from May 1, two weeks prior to the consistent annual total thyroxine (TT<sub>4</sub>) peak in mid-May, until the last sampling date. Plasma was obtained at two sampling dates from control and PTU -treated coho salmon: May 15, during the plasma TT<sub>4</sub> peak; and May 26, after the TT<sub>4</sub> peak. Radioimmunoassays were used to measure plasma TT<sub>4</sub>, total triiodothyronine (TT<sub>3</sub>), free thyroxine (FT<sub>4</sub>), and salmon growth hormone (sGH). The PTU -treatment inhibited the natural smoltification-related increases in plasma TT<sub>4</sub>, TT<sub>3</sub> and GH levels compared with controls, but PTU-treatment did not affect these hormone levels when they were low. PTU -treatment increased FT<sub>4</sub> and decreased TT<sub>3</sub> and sGH levels in the May 26 sample. In the May 15 sample, FT<sub>4</sub> levels were unaffected by PTU-treatment, whereas TT<sub>4</sub> levels were decreased. These data demonstrate the ability of PTU to induce hypothyroidism in salmonids as shown by the decrease in TT<sub>4</sub> and TT<sub>3</sub>. These data demonstrate that PTU treatment by immersion can induce hypothyroidism in salmonids as shown by: (1) the inhibition of the natural increases of TT<sub>4</sub> and TT<sub>3</sub>; (2) the increase in FT<sub>4</sub> levels corresponding to the lowered TT<sub>3</sub> levels, suggesting an inhibition of thyroxine 5′-monodeiodinase activity. We also show for the first time that PTU treatment can lower plasma GH levels in salmonids. This lowering of plasma GH level is associated with the decrease in TT<sub>3</sub> levels and the increase in FT<sub>4</sub> levels. Lhe PLU induced lowering in GH levels may contribute to the observed changes in FT<sub>4</sub> and TT<sub>3</sub>, since GH is known to increase thyroxine 5′-monodeiodinase activity.</p>}},
author = {{Ebbesson, L. O.E. and Björnsson, B. Th and Stefansson, S. O. and Ekström, P.}},
issn = {{0920-1742}},
keywords = {{Development; Equilibrium dialysis; Fish; Hypothyroid; Immersion; Radioimmunoassay; Smoltification; Teleost; Thyroid hormones}},
language = {{eng}},
month = {{12}},
number = {{4}},
pages = {{305--313}},
publisher = {{Springer}},
series = {{Fish Physiology and Biochemistry}},
title = {{Propylthiouracil-induced hypothyroidism in coho salmon, Oncorhynchus kisutch : Effects on plasma total thyroxine, total triiodothyronine, free thyroxine, and growth hormone}},
volume = {{19}},
year = {{1998}},
}