[Thyroxine deiodination in the fetus].
T4 deiodination has been studied using the fetal liver and kidney of miniature goats during late pregnancy. They were homogenized in 0.15M phosphate buffer, pH7.4 to make 25% homogenate which was incubated with outer ring labeled 125I-T4, 125I-rT3 or inner ring labeled 125I-T4 at 37 degrees C for 15, 30, 60, 90 or 120 min. either with or without 20mM DTT. After incubation they were extracted in ethanol and subjected to TLC to separate 125I-compounds. The radioactivity of each compound was measured and its production rate was expressed as a percentage of total radioactivity of the extract. The activity of deiodination in the outer ring of T4 in fetal liver was similar to that observed in the mother's . Fetal kidney showed a markedly increased activity in deiodination in the inner ring compared to that of all the other tissues studied. In contrast it showed the lowest deiodination in the outer ring. The addition of 20mM DTT had little effect on T4 deiodination in fetal organs. These data indicate a significant difference between T4 deiodinating activity in the liver and kidney of the fetus. It is felt that the kidney plays a more important role in T4 deiodination than the liver during fetal life.
D000818:Animals; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006041:Goats; D007455:Iodine / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D013974:Thyroxine / Q000378:metabolism*
D007455:Iodine; D013974:Thyroxine