Uptake of L-tri-iodothyronine by human cultured trophoblast cells.
We investigated the uptake of L-tri-iodothyronine (T3) by cultured human trophoblast cells. Uptake was time-dependent, initially linear and approaching equilibrium after 60 min with an approximate half-time of 13 +/- 4.5 min (mean +/- S.E.M., n = 4). It had a non-saturable component accounting for about 50% of total uptake. We demonstrated a single saturable T3 uptake mechanism with a calculated Michaelis constant (Km) of 755 +/- 145 nmol/l (n = 11-13) and a corresponding maximum velocity of 28.8 +/- 5.3 pmol/min per mg protein (n = 11-13). The Km value was similar to those reported in other tissues.
Mitchell
A M
AM
Conjoint Internal Medicine Laboratory, Royal Brisbane Hospital, Queensland, Australia.
Manley
S W
SW
Mortimer
R H
RH
D002478:Cells, Cultured; D006801:Humans; D007457:Iodine Radioisotopes; D013997:Time Factors; D014284:Triiodothyronine / Q000493:pharmacokinetics*; D014327:Trophoblasts / Q000378:metabolism*
D007457:Iodine Radioisotopes; D014284:Triiodothyronine