Deiodination activity in extrathyroidal tissues of the Atlantic hagfish, Myxine glutinosa
DOIAbstract
We measured low substrate (<1 nM) thyroid hormone (TH) deiodination activities in liver, muscle, intestine, and brain microsomes of Atlantic hagfish fasted for 2 weeks and found extremely low thyroxine (T-4) outer-ring deiodination (T4ORD) and inner-ring deiodination (T4IRD) as well as 3,5,3'-triiodothyronine (T-3) IRD activities. T3ORD, 3',5'-triiodothyronine (rT(3)) ORD and rT(3)IRD activities were undetectable. Hagfish deiodinating pathways resembled those of teleosts in requiring a thiol cofactor (dithiothreitol, DTT) and in their inhibition by established deiodinase inhibitors and by TH analogues. However, under optimal pH and DTT conditions intestinal T4ORD activity exceeded that of liver about 10-fold. This contrasts with the situati...
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