MEMBRANE-TRANSPORT OF L-TRIIODTHYRONINE BY HUMAN RED-CELL GHOSTS

L-T3 transport has been investigated in human red cell ghosts. Determination of initial T3 uptake revealed two separate saturable uptake systems, one with a Km of 1.6 × 10-8M, the other with a Km of 3.3 × 10-6M. Binding experiments resulted in two dissociation constants, 1.4 × 10-7M.and 2.6 × 10-6M. Uptake was dependent on the ghost volume, indicating an intravesicular location of T3. The T3 was concentrated 6 times by the ghosts. Ouabain reduced the uptake by the low Km system, but was without effect on the high Km system. Thus evidence is provided both of binding of T3 to the ghost membrane and of its uphill transport across the membrane. © 1979.