Thyroxine transport

Pizzagalli, F., et al. Identification of a novel human organic anion transporting polypeptide as a high affinity thyroxine transporter. Mol. Endocrinol. 2002, 36, 2283-2296. 

Oatplc/OATPICI, of Oatpl/OATPl subfamily c , is the brain specific isoform and has been considered to be involved in the thyroid hormone (thyroxine) transport (105-107). 

Structurally Specific Binding of Halogenated Biphenyls to Thyroxine Transport Protein. 

Schreiber G, Aldred AR, Jaworowski A, Nilsson C, Achen MG, Segal MB. Thyroxine transport from blood to brain via transthyretin synthesis in choroid plexus. Am J Physiol 1990 258 R338,1990. 

Riley, W.W. and J.G. Eales. Characterization of L-thyroxine transport into hepatocytes isolated from juvenile rainbow trout (Oncorhynchus mykiss). Gen. Comp. Endocrinol. 90 31-42, 1993. 

Q.26.12 Identical amounts of thyroxine transport protein (TTR) are placed in water and gasoline. Identical sedimentation experiments are run on both samples. It s discovered tliat TTR sediments faster in water what is a likely explanation of this observation ... 

A possible explanation for the highly selective retention of the OH-PCBs in blood may be their structural resemblance with thyroxin. Both rats and mice metabolize PCB 77 by CYPIA to the 1,2-shift metabolite, 4-OH-3,5,3, 4 -PCB, 5-OH 3,3, 4,4 -PCB, and 6-OH-3,3, 4,4 -PCB (McKinley et al. 1993 Morse et al. 1995). Only the 4-OH metabolite was selectively retained, with blood containing 4-OH-3,5,3, 4 -PCB at a concentration 15 times higher than the parent compound, 5 days after oral exposure to PCB 77 in mice (Bergman et al. 1994). This metabolite was found to be bound to a thyroxin-transporting protein (transthyretin) in the blood (Brouwer et al. 1986). Competitive binding studies of OH-PCBs relative to T4 and computer modeling showed that OH-PCBs with the substituents in meta or para positions were much more effective competitors for T4 than if the substituents were bound in an ortho position (Rickenbacher et al. 1986). 

Chauhan KR, Kodavanti PRS, McKinney JD. 2000. Assessing the role of ortfto-substitution on polychlorinated biphenyl binding to transthyretin, a thyroxine transport protein. Toxicol Appl Pharmacol 162 10-21. 

Rickenbacher U, McKinney JD, Oatley SJ, et al. 1986. Structurally specific binding of halogenated biphenyls to thyroxine transport protein. J Med Chem 29 641-648. 

Albumin also binds thyroxine (RIO), but its binding afiinity is considerably less than is that of TBG, and therefore albumin plays less of a role in thyroxine transport. 

The Role of Thyroxine-Binding Froteins in Thyroxine Transport and Turnover... 

In another critical study, it was observed that thyroid hormone does indeed cross the placenta. Therefore, if insufficient iodine is available to the mother it results in reduced maternal synthesis of thyroid hormone with insufficient placental thyroxine transport for fetal requirements. 

W. H. Sawyer, and G. Schreiber, Thyroxine transport in choroid plexus, J. Biol. Chem. 262 13907 (1987). 

At least five different steps can be distinguished in iodine metabolism in the thyroid (1) trapping of iodine by the thyroid s iodine pump, (2) oxidation and organic fixation of the iodine, (3) storage of the hormone, (4) release of the hormone, and (5) thyroxine transport to the target organ. 

Cao J, Lin Y, Guo L, Zhang A, Wei Y, Yang Y, et al. Structure-based investigation on the binding interaction of hydroxylated polybrominated diphenyl ethers with thyroxin transport proteins. Toxicol 2010 277 20-8. 

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