Vol. 277, Issue 5, E915-E919, November 1999
Fetal-to-maternal transfer of 3,3',5-triiodothyronine
sulfate and its metabolite in sheep
Sing-Yung
Wu1,
Daniel H.
Polk2,
Wen-Sheng
Huang3, and
Delbert A.
Fisher2
1 Nuclear Medicine and Medical
Services, Department of Veterans Affairs Medical Center, Long Beach
90822; 2 Perinatal Laboratory,
Harbor-University of California Los Angeles Medical Center, Torrance,
California 90509; and 3 Department
of Nuclear Medicine, Tri-Service General Hospital, Taipei, Taiwan 107, China
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
(T3) sulfate
(T3S), 3,3'-diiodothyronine
sulfate (T2S), and
T3 concentrations in fetal serum
and in maternal serum and urine after
T3S infusion to the fetus
(n = 5) or the ewe
(n = 6). Maternal infusion of
T3S did not increase fetal serum
T2S,
T3S, or
T3 concentrations. In contrast, fetal infusion of T3S produced
significant increases in maternal serum
T2S and
T3S but not
T3 concentrations. Fetal
T3S infusion also increased
maternal urine excretion of T3S.
However, the 4-h cumulative maternal urinary excretion of
T2S and
T3S after fetal T3S infusion was less than the
excretion observed after fetal infusion of equimolar amounts of
T3 in our previous study. It is
concluded that fetal serum T2S and
T3S can be transferred to maternal
compartments. However, compared with
T3, these sulfoconjugates may be
less readily transferred.
sulfoconjugate; thyroid hormone metabolism
