High affinity L-triiodothyronine binding sites on washed rat erythrocyte membranes.
Two orders of saturable binding sites for L-triiodothyronine were found on washed rat erythrocyte membranes. The high affinity, low capacity site showed values of Kd 0.19 X 10(-10) M. This value was in the range of concentration of free L-triiodothyronine found in the plasma and was several orders of magnitude higher than the Kd values previously reported for other L-triiodothyronine membrane-binding systems. The binding site also showed a high stereospecificity for L-triiodothyronine. D-3,5,3'-triiodothyronine and L-thyroxine were less potent (about 1000-fold) than L-triiodothyronine in competing for these sites. L-3,3,5'-triiodothyronine and triiodothyroacetic acid were inactive. The physiological relevance of this site is considered.
D000818:Animals; D001667:Binding, Competitive; D004910:Erythrocyte Membrane / Q000378:metabolism* / Q000648:ultrastructure; D004912:Erythrocytes / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine / Q000097:blood*
D011956:Receptors, Cell Surface; D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine