3,5,3 -Triiodo-L-thyronine

PNP-DTP has been used to photoaffinity label the thyroid hormone nuclear receptors in intact cells by preparing a derivative of 3,5,3 -triiodo-L-thyronine with the crosslinker (Pascual et al., 1982 Casanova et al., 1984). Effective photoreactive conjugation was found to occur after irradiation with UV light at 254 or 310 nm. 

Lee, C.G. and Ip, Y.K. (1987). Environmental effect on plasma thyroxine (T4), 3,5,3 -triiodo-L-thyronine (T3), prolactin and cyclic adenosine 3 -5 -monophosphate (cAMP) content in the mudskippers Periophthalmus chrysospilos and Boleophthalmus boddaerti. Comparative Biochemistry and Physiology 87A, 1009-1014. 

Fok, P., J.G. Eales and S.B. Brown. Determination of 3,5,3 -triiodo-L-thyronine (T3) levels in tissues of rainbow trout (Salmo gairdneri) and the effect of low ambient pH and aluminum. Fish Physiol. Biochem. 8 281-290, 1990. 

McLeese, J.M. and J.G. Eales. Characteristics of the uptake of 3,5,3 -triiodo-L-thyronine and L-thyroxine into red blood cells of rainbow trout, Oncorhynchus mykiss. Gen. Comp. Endocrinol. 103 200-208, 1996. 

Despite the fact that they can be much more reactive than nitrenes, carbene derivatives are less frequently cited in reports on photoaffinity labels. Two such derivatives of thyroid hormone have been described in which the amino group of the alanine side chain of 3,5,3 -triiodo-L-thyronine or 3,5,3, 5 -tetraiodo-L-thyronine was derivatized with 2-diazo-3,3,3-trifluoropropionate (246). Irradiation at 254 nm of these compounds with several cell lines yielded low incorporation of reagent (0.5-13.5%) into two forms of thyroid hormone receptor proteins. Low incorporation was also characteristic of early reports of photoaffinity labeling (e.g., 247) in which 0 -ethyl-2-diazomalonyl-cAMP and A, C)2. (ji(ethyl-2-diazomalonyl)-cAMP were used to generate carbenes which modify rabbit muscle phosphofructokinase. Similarly, only 3-14% of the potential sites of lactate dehydrogenase were labeled by the carbene derived from 3-(3//-diazirino)pyridine adenine dinucleotide (248). 

One of the most frequent questions asked has been whether or not pure ID results in hypothyroidism (Morreale de Escobar et ai, 1997). The answer to this is especially difficult, because there are few quantitative indices of thyroid hormone action in different tissues. For this reason, we have focused on concentrations of 3,5,3 -triiodo-L-thyronine (T3), which was taken as an index of possible thyroid hormone effectiveness at the individual tissue level, as discussed elsewhere (Escobar-Morreale et ai, 1995). As will be seen, the thyroid status of rats with ID cannot be defined for the animal as a whole, because it is eminently tissue specific At all grades of ID, elevated. 

The rat brain c-erb-A polypeptides generated in vitro bound [I25l] 3 5,3-triiodo-L-thyronine with a dissociation constant of 3 X 10" Mt approximating the binding affinity for the thyroid hormone receptor isolated from tissue culture cells (36, 3. Competition for th various thyroid hormone... 

A. Pontecorvi, M. Lakshmanan and J. Robbins, Intracellular transport of 3,5,3 -triiodo-L thyronine in rat skeletal myoblasts. Endocrinology 121 2145-2152 (1987). 

Triiodo-L-thyronine contents of rat embryonic tissues before and after onset of fetal thyroid function. Endocrinology 118 1259 (1986)... 

Escobar del Rey F, Pastor R, Mallol J, Morreale de Escobar G, Effects of maternal iodine deficiency on the L-Thyroxine and 3,5,3 -Triiodo-L-Thyronine contents of rat embryonic tissues before and after onset of fetal thyroid function. Endocrinology 118 1259 (1986)... 

Cl5H18N2O5, Benzyloxycarbonylglycyl-DL-proline, 44B, 441 Cl5H18N2O5, Benzyloxycarbonylglycyl-L-proline, 43B, 616 Cl5H19CII3NO7, 3,5,3 -Triiodo-L-thyronine hydrochloride trihydrate,... 

C15H29N5O7, Cyclopentasarcosyl dihydrate, 39B, 363 Cl gHi 3NOi,, N,N-Bis(2-hydroxyethyl)glycine, 43B, 617 Cl sHi al aNOi, 3,5,3 -Triiodo-L-thyronine methyl ester, 41B, 551 C16H18N2O2, Clavicipitic acid, 46B, 485... 

The iodinated amino acids which have been identified to date in the thyroid gland are 3-monoiodo-L-tyrosine or MIT (8,38,40,62), 3,5-diiodo-L-tyrosine or DIT (9,20), 3,5,3 -triiodo-L-thyronine or TRITh (17,41,42), 3,5,3, 5 -tetraiodo-L-thyronine or thyroxine or Tx (19,24), and 2 (or 4)-monoiodo-L-histidine or MIH (43). TRITh and Tx are the two constituents of the thyroid hormone MIT and DIT are their precursors. The formation of all of these iodo derivatives during the hormone genesis, their secretion, the circulation of some of them in blood, and their metabolism can be followed by radiochromatography and, for certain problems, by paper electrophoresis. 

The elution of radioactive spots of a chromatogram can be used for purification, or even for isolation purposes. The general techniques are applied (3,41) using radioactivity controls. The recovery of is nearly quantitative, but the use of eluates to establish radiochromati rams has no advantage over direct measurements on the spots. No special tech niques have been elaborated for radioactive substances in this field, but the efficiency of the procedure has been shown by the recent isolation of 3,5,3 -triiodo-L-thyronine (41). 

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