Fetal-to-maternal transfer of 3,3',5-triiodothyronine sulfate and its metabolite in sheep

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Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings
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Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings

Published on: October 25, 2015

S Y Wu1, D H Polk, W S Huang

  • 1Nuclear Medicine Services, Department of Veterans Affairs Medical Center, Long Beach, California 90822, USA. sywu@pop.long-beach.va.gov

The American Journal of Physiology
|November 24, 1999
PubMed

Earlier studies have shown that sulfoconjugation is a major pathway of thyroid hormone metabolism in fetal mammals. To assess the placental transfer of sulfoconjugates in the pregnant sheep model, we measured 3,3',5-triiodothyronine (T(3)) sulfate (T(3)S), 3, 3'-diiodothyronine sulfate (T(2)S), and T(3) concentrations in fetal serum and in maternal serum and urine after T(3)S infusion to the fetus (n = 5) or the ewe (n = 6). Maternal infusion of T(3)S did not increase fetal serum T(2)S, T(3)S, or T(3) concentrations. In contrast, fetal infusion of T(3)S produced significant increases in maternal serum T(2)S and T(3)S but not T(3) concentrations. Fetal T(3)S infusion also increased maternal urine excretion of T(3)S. However, the 4-h cumulative maternal urinary excretion of T(2)S and T(3)S after fetal T(3)S infusion was less than the excretion observed after fetal infusion of equimolar amounts of T(3) in our previous study. It is concluded that fetal serum T(2)S and T(3)S can be transferred to maternal compartments. However, compared with T(3), these sulfoconjugates may be less readily transferred.

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