Deiodination activity in extrathyroidal tissues of the Atlantic hagfish,Myxine glutinosa

Abstract

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 (T 4 ORD) and inner-ring deiodination (T 4 IRD) as well as 3,5,3′-triiodothyronine (T 3) IRD activities. T 3 ORD, 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 T 4 ORD activity exceeded that of liver about 10-fold. This contrasts with the situation in teleosts but resembles that reported recently in larval and adult lampreys, suggesting the intestine as a primary site of TH deiodination in lower craniates.

Iodothyronine deiodinase structure and function: from ascidians to humans

“…In vivo deiodination of T 4 was shown in the ascidian Phallusia mammillata already in 1989 (Leloup & Seugnet 1989). Approximately 10 years later, in vitro studies using low nanomolar substrate concentrations showed the presence of T 4 ORD, T 4 IRD and T 3 IRD in a primitive vertebrate, the sea lamprey (Petromyzon marinus) and in the invertebrate Atlantic hagfish (Myxine glutinosa) (Eales et al 1997, 2000, McLeese et al 2000. For both species the highest activity was found in the intestine.…”

“…01 mM PTU and T 4 ORD was 60% inhibited by 0 . 1 mM PTU, while T 3 IRD was unaffected by 1 mM PTU (McLeese et al 2000). Unfortunately, no deiodinases have yet been cloned from hagfishes, which are the closest living relatives to the present vertebrates, or from lampreys, which are considered the most primitive vertebrates as shown in the simplified evolutionary tree of the Deuterostomia in Fig.…”

Ο ρόλος του θυρεοειδή κατά την οντογένεση και την αναστροφή του φύλου στην τσιπούρα (Sparus aurata)

“…Μία ιδιαιτερότητα του DIO1 των τελεόστεων που έχουν μελετηθεί μέχρι σήμερα -μεταξύ αυτών και η τσιπούρα -είναι ότι δεν καταστέλλεται η δράση της από το φάρμακο propylthiouracil (PTU), που ισχύει για την αντίστοιχη πρωτεΐνη των θηλαστικών (Sanders et al, 1997;Cyr et al, 1998;Bianco et al, 2002;Orozco et al, 2003;. , Frith & Eales, 1996Orozco et al, 1997Orozco et al, , 2000Orozco et al, , 2003Mol et al, 1998;Sanders et al, 1999;McLeese et al, 2000;Gereben et al, 2002;Sutija et al, 2003;Garcia-G et al, 2004;Walpita et al, 2007). απάντηση (Evans, 1988;Brent, 1994;Tsai & O'Malley, 1994;Zhang & Lazer, 2000).…”