Stimulation of hepatic thyroxine 5'-deiodinase activity in rainbow trout (Oncorhynchus mykiss) by Pacific salmon growth hormone.
1. Growth hormone extracted from Pacific salmon pituitaries (sGH) was injected intra-peritoneally into rainbow trout to determine sGH effects on plasma levels of thyroxine (T4), 3,5,3'-triiodothyronine (T3) and properties of the hepatic 5'-deiodinase enzyme (5'-D) responsible for T4 to T3 conversion. 2. After 24 hr, sGH (0.1 or 0.5 microgram/g) did not alter the plasma T4 level or 5'-D, Km, but elevated plasma T3 and especially 5'-D Vmax. 3. Thus sGH, like the previously tested human GH, acutely enhances the potential for extra-thyroidal T3 production in trout by increasing the functional level of hepatic 5'-D, but without changing the plasma T4 level.
Department of Zoology, University of Manitoba, Winnipeg, Canada.
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MacLatchy
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Kawauchi
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Eales
D000818:Animals; D004789:Enzyme Activation; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D007453:Iodide Peroxidase / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D012474:Salmon / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014337:Trout / Q000378:metabolism*
D014284:Triiodothyronine; D013006:Growth Hormone; D007453:Iodide Peroxidase; D013974:Thyroxine