PMID- 9415064
OWN - NLM
STAT- MEDLINE
DCOM- 19980202
LR  - 20190709
IS  - 0022-0795 (Print)
IS  - 0022-0795 (Linking)
VI  - 155
IP  - 2
DP  - 1997 Nov
TI  - Divergent deiodination of thyroid hormones in the separated parts of the fetal 
      and maternal placenta in pigs.
PG  - 295-303
AB  - Previous work from this laboratory has shown that the thyroid gland of the fetal 
      pig begins to function at about day 46-47 (0.40-0.415 fraction of gestational 
      age). Sera from fetuses contain lower thyroxine (T4), 3,3',5-triiodothyronine 
      (T3) and 3,3',5'-triiodothyronine (rT3) concentrations than maternal sera, except 
      for about 2 weeks before term. The fetal T4 metabolism is dominated by the 
      5'-monodeiodinating activity (5'-MD). In the present study we measured the 
      iodothyronines content, and the outer (5'-MD) and inner (5-MD) monodeiodinases 
      activity, in homogenates of the placenta. The pig placenta, which is of the 
      epitheliochorial type, was separated into the fetal and the maternal part. The 
      concentrations of T4, T3 and rT3 were lower, and the deiodinating activity of 
      5'-MD and 5-MD higher, in the fetal than in the maternal placenta. The fetal 
      placenta not only deiodinated more actively T4 to T3 and T4 to rT3, but degraded 
      T3 to 3,3'-diiodothyronine (3,3'-T2) more actively than rT3 to 3,3'-T2. Such 
      divergent deiodinating activity of T4 to T3, T3 to 3,3'-T2 and rT3 to 3,3'-T2 
      might favor establishing a relatively high and constant rT3 concentrations in 
      fetal and maternal placentas, and a lower T3 in the fetal placenta. The inner 
      ring deiodinating activity (excluding a day before parturition) was always more 
      active in the fetal placenta, while the outer ring deiodinations varied in this 
      respect, depending on the gestation stage. These results support the hypothesis 
      that in the fetal pig, enzymatic deiodination of thyroid hormones forms a barrier 
      which reduces transplacental passage of the hormones and that the fetal part of 
      the placenta is the primary factor in the mechanism regulating the hormonal 
      transfer. In spite of the presence of the barrier, there is an adequate maternal 
      supply of thyroid hormones to the fetus in early gestation, which suggests that 
      the enzymatic mechanism is influenced in some way by the thyroid status of the 
      fetus.
FAU - Krysin, E
AU  - Krysin E
AD  - Department of Developmental and Experimental Endocrinology, Polish Academy of 
      Sciences, Poznan, Poland.
FAU - Brzezinska-Slebodzinska, E
AU  - Brzezinska-Slebodzinska E
FAU - Slebodzinski, A B
AU  - Slebodzinski AB
LA  - eng
PT  - Journal Article
PL  - England
TA  - J Endocrinol
JT  - The Journal of endocrinology
JID - 0375363
RN  - 0 (Diiodothyronines)
RN  - 0 (Thyroid Hormones)
RN  - 06LU7C9H1V (Triiodothyronine)
RN  - 5817-39-0 (Triiodothyronine, Reverse)
RN  - EC 1.11.1.8 (Iodide Peroxidase)
RN  - Q51BO43MG4 (Thyroxine)
SB  - IM
MH  - Animals
MH  - Diiodothyronines/analysis/metabolism
MH  - Female
MH  - Fetus/metabolism
MH  - Iodide Peroxidase/analysis/*metabolism
MH  - Placenta/enzymology/*metabolism
MH  - Pregnancy
MH  - Pregnancy, Animal/*metabolism
MH  - Radioimmunoassay
MH  - Swine/*metabolism
MH  - Thyroid Hormones/analysis/*metabolism
MH  - Thyroxine/analysis/metabolism
MH  - Triiodothyronine/analysis/metabolism
MH  - Triiodothyronine, Reverse/analysis/metabolism
EDAT- 1998/01/01 00:00
MHDA- 1998/01/01 00:01
CRDT- 1998/01/01 00:00
PHST- 1998/01/01 00:00 [pubmed]
PHST- 1998/01/01 00:01 [medline]
PHST- 1998/01/01 00:00 [entrez]
AID - 10.1677/joe.0.1550295 [doi]
PST - ppublish
SO  - J Endocrinol. 1997 Nov;155(2):295-303. doi: 10.1677/joe.0.1550295.