Hepatic and branchial thyroid hormone deiodinase activities associated with the parr-smolt transformation of coho salmon (Oncorhynchus kisutch)
| Autor: | B.A. McKeown, J.G. Eales, George Alexander, R.M. Sweeting |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Gills
medicine.medical_specialty Thyroxine deiodinase Population Deiodinase Iodide Peroxidase chemistry.chemical_compound Endocrinology Internal medicine medicine Animals education Chromatography High Pressure Liquid Smoltification education.field_of_study biology Thyroid Body Weight Sodium Organ Size Oncorhynchus kisutch Water-Electrolyte Balance biology.organism_classification Kinetics medicine.anatomical_structure chemistry Liver Thyronine biology.protein Microsomes Liver Oncorhynchus Triiodothyronine Animal Science and Zoology Hormone |
| Zdroj: | General and comparative endocrinology. 94(2) |
| ISSN: | 0016-6480 |
| Popis: | Plasma 3,5,3′-triiodo- l -thyronine (T 3 ) concentrations, liver and gill thyroid hormone deiodinase activities, growth parameters, and hypoosmoregulatory capacity were measured for an outdoor population of freshwater, hatchery-reared yearling coho salmon prior to, during, and after the parr-smolt transformation. The plasma Na + response to a 24-hr seawater (30 ppt) challenge showed characteristic smolt hypoosmoregulatory capacity only from mid-May to mid-June. Increases in growth parameters (body weight and length) were curbed during this time. Two peaks in plasma T 3 occurred in late April and early May. Both liver and gill T 4 ( l -thyroxine) outer-ring 5′-monodeiodinase (T 4 5′D) activities, converting T 4 to T 3 , fell from March to June, with no biologically meaningful overall correlation with plasma T 3 . However, T 4 5′D activity of gill and liver did increase in presmolts in late May, coinciding with an elevation in plasma T 3 . Hepatic inner-ring T 4 5D activity, converting T 4 to 3,3′,5′-T 3 (rT 3 = reverse T 3 ), was lower in smolts than in presmolts. Activity of hepatic outer-ring T 3 5′D, which converts T 3 to 3,5-T 2 , was negligible, but activity of hepatic inner-ring T 3 5D, which produces 3,3′-T 2 from T 3 , was higher in early smolts than in postsmolts. We conclude that hepatic deiodinase activities of smolting coho salmon may act to maintain hepatic and plasma T 3 at modest levels and that the branchial production of T 3 appears to parallel that of the liver. |
| Databáze: | OpenAIRE |
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