[Characteristics of specific binding of thyroid hormones with plasma membranes of syncytiotrophoblast of human placenta].
Kinetic and equilibrium characteristics of the interaction of triiodothyronine (T3) and its structural analogues with plasmatic membranes of human placental syncytiotrophoblast were studied. The specific binding was temperature-dependent, saturable, reversible, selective and stereospecific. The following values of the binding parameters were obtained: association rate constant--1.0 x 10(10) M-1min-1, dissociation rate constant (fast phase)--2.4 x 10(-1) min-1, half-life time of the complex--2.9 min, equilibrium association constants for high- and low-affinity sites--2.0 x 10(10) M-1 and 4.8 x 10(6) M-1, respectively, concentrations of the corresponding sites--12.5 fmol and 36.0 pmol per mg of membrane protein, respectively. The affinity for membranes decreased in the following order: L = T3 greater than L = T4 greater than 3,3,5-triiodothyroacetic acid greater than 3,3,5-triiodothyropropionic acid greater than D = T3 greater than D = T4 greater than 3,5-diiodo-L-tyrosine.
Karpyza
E I
EI
Ermolenko
M N
MN
Sviridov
O V
OV
D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D007700:Kinetics; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D014284:Triiodothyronine / Q000378:metabolism*
D014284:Triiodothyronine
Kharakteristika spetsificheskogo sviazyvaniia tireoidnykh gormonov s plazmaticheskimi membranami sintsitiotrofoblasta platsenty cheloveka.