Immersion of rainbow trout in 3,5,3'-triiodo-L-thyronine (T3): effects on plasma T3 levels and hepatic nuclear T3 binding.
An immersion protocol was established for chronically administering thyroid hormone to fish. Rainbow trout were immersed in solutions of 3,5,3'-triiodo-L-thyronine (T3) at 11 degrees C for various periods. Most plasma T3 adjustment occurred by 24 hr and within 5 days consistent plasma T3 levels were observed. Availability of unoccupied hepatic nuclear T3-binding sites was assessed in two experiments by uptake of nuclear radioactivity in T3-immersed trout injected 12 hr previously with [125I]T3. At low ambient T3 levels over 92% of nuclear radioactivity was identified chromatographically and immunologically as T3, but at high ambient levels (25 micrograms/100 ml) biliary [125I]T3 metabolites may contaminate the nuclear fraction. Displacement of [125I]T3 from nuclei was first detected at 0.25 micrograms T3/100 ml water, corresponding to a plasma T3 level of 0.55 ng/ml; maximum displacement, depending on experiment, occurred at 1.25 and 3.8 micrograms T3/100 ml, corresponding to plasma T3 levels of 14 and 9 ng/ml. In conclusion, chronic physiologic T3 treatment of these trout can be achieved by immersion in T3 solutions of 0.1-5 micrograms T3/100 ml water.
Omeljaniuk
R J
RJ
Eales
J G
JG
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002850:Chromatography, Gel; D008099:Liver / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone; D012487:Salmonidae / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*; D014337:Trout / Q000097:blood*
D011956:Receptors, Cell Surface; D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine