title: Effect of sodium molybdate on the thyroxine-binding affinity of transport cytosol proteins.
abstract: The presence of sodium molybdate during tissue homogenization is known to increase the number of cytosol binding sites for glucocorticoids, progesterone, androgens and oestrogens. We wondered whether a phenomenon similar to this stabilization of steroid receptors would also occur in thyroxine-binding cytosol protein. We found that the presence of sodium molybdate (10 mmol/l) in rat adenohypophyseal cytosol increased its thyroxine-binding capacity by up to 96%. In the case of binding protein cytosol minus molybdate, Ka = 5.5 X 10(9) l.mol-1, whereas for cytosol plus molybdate Ka(1) = 6.0 X 10(9) l.mol-1 and Ka(2) = 3.0 X 10(10) l.mol-1. Cytosol prepared without molybdate did not contain a binding protein class with a higher Ka. The effect is stereo-specific and the LT4 bond is not displaced by DT4.
mesh_terms: D000818:Animals; D003600:Cytosol / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008982:Molybdenum / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013974:Thyroxine / Q000378:metabolism*; D013975:Thyroxine-Binding Proteins / Q000378:metabolism*
chemical_list: D013975:Thyroxine-Binding Proteins; D008982:Molybdenum; C024687:sodium molybdate(VI); D013974:Thyroxine