Influence of bovine TSH on plasma thyroxine levels and thyroid function in brook trout, Salvelinus fontinalis (Mitchill)

Chan, H.H.; Eales, J.G.

General and Comparative Endocrinology 28(4): 461-472

1976


ISSN/ISBN: 0016-6480
PMID: 60268
DOI: 10.1016/0016-6480(76)90155-6
Accession: 068518945

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Abstract
The influence of i.v. injected bovine thyroid stimulating hormone (TSH) on the plasma thyroxine (T4) level was studied in 1 and 2 yr old brook trout acclimated at 10-12.degree. Plasma T4 was highest between 9 and 48 h after a single TSH injection. The plasma T4 response to TSH was uninfluenced by nutritional state, anesthesia, type of injection vehicle or ACTH and was of similar magnitude at 5, 12 or 20.degree. The response decreased if daily injections extended beyond 5 days. Large fish were more responsive than small fish of the same age to a TSH dose standardized for body weight. A linear relationship existed between log TSH dose and plasma T4 of intact trout. The precision index was superior to that for other TSH assays involving fish. Radioiodine indices of thyroid activity (plasma PB125I, CR ) and bile organic 127I content were linearly related to log TSH dose with good precision. Thryoid uptake of 125I was an ambiguous and less precise assay for TSH. An attempt was made to define a physiologic TSH dose to administer to trout.