[Simulating and inhibiting effect of individual blood serum transport proteins on thyroid hormone binding with human placental cell membrane].

Binding processes in in vitro systems modelling specific interactions between transport and receptor proteins, thyroid hormones of human placental tissue and the washing blood, have been studied. These systems included syncytiotrophoblast villous membranes, thyroxine (T4), triiodothyronine (T3) and iodothyronine-binding proteins: transthyretin, albumin, immunoglobulins (Ig) M and G, apolipoprotein A-I, and the T4-binding globulin purified from human retroplacental serum. All of the transport proteins at concentrations close to the Ka values of their complexes with thyroid hormones produced inhibitory effects on the binding of [125I]T3 or [125I]T4 to the thyroid hormone membrane receptor.

[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.

[Thyroxine-binding globulin and its molecular variant in human amniotic fluid].

Total thyroxine--binding globulin (TBGt) and its pregnancy-associated molecular variant (TBG-1) were detected by radioimmunoassay in human amniotic fluid collected at the time of delivery. TBGt purified from amniotic fluid by affinity chromatography and hydroxylapatite chromatography, displayed electrophoretic properties, immunoreactivity, a molecular mass, affinity for thyroxine and TBG-1 content identical to those of pure TBGt from human pregnancy serum. The concentrations of TBGt and TBG-1 in maternal venous blood serum were 49 +/- 7 mg/ml and 3.

[Blood levels of molecular variants of human thyroxine-binding globulin].

The concentrations of the molecular variant of the thyroxine-binding globulin (TBG-1) and total TBG were measured in normal human sera (male and female), venous blood sera at various stages of normal pregnancy as well as in matched samples of retroplacental and venous sera of mothers and in cord sera of their newborns. It was shown that TBG-1 appeared on the 6th-11th week of pregnancy and its level increased up to the delivery. A TBG-1 portion in the total TBG content increased from 2.