Regulation of iodide uptake in placental primary cultures.
BACKGROUND
Maintenance of adequate iodide supply to the developing fetus is dependent not only on maternal dietary iodine intake but also on placental iodide transport. The objective of this study was to examine the effects of different pregnancy-associated hormones on the uptake of radioiodide by the placenta and to determine if iodide transporter expression is affected by hormone incubation.


METHODS
Primary cultures of placental trophoblast cells were established from placentas obtained at term from pre-labor caesarean sections. They were pre-incubated with 17β-estradiol, prolactin, oxytocin, human chorionic gonadotropin (hCG) and progesterone either singly or in combination over 12 h with (125)I uptake being measured after 6 h. RNA was isolated from placental trophoblasts and real-time RT-PCR performed using sodium iodide symporter (NIS) and pendrin (PDS) probes.


RESULTS
Significant dose response increments in (125)I uptake by trophoblast cells (p < 0.01) were observed following incubation with hCG (60% increase), oxytocin (45% increase) and prolactin (32% increase). Although progesterone (50-200 ng/ml) and 17β-estradiol (1,000-15,000 pg/ml) alone produced no significant differences in uptake, they facilitated increased uptake when combined with prolactin or oxytocin, with a combination of all four hormones producing the greatest increase (82%). Increased (125)I uptake was accompanied by corresponding increments in NIS mRNA (ratio 1.52) compared to untreated control cells. No significantly increased expression levels of PDS were observed.


CONCLUSIONS
Pregnancy-associated hormones, particularly oxytocin and hCG, have a role in promoting placental iodide uptake which may protect the fetus against iodine deficiency.
UCD School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.
R
R
Burns
UCD School of Medicine and Medical Science, University College Dublin, Dublin, Ireland ; National Maternity Hospital, Dublin, Ireland.
C
C
O'Herlihy
UCD School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.
P P A
PP
Smyth
Iodide transporters; Iodide uptake; Placenta; Pregnancy