Binding of the sulfates of estradiol-17beta to human serum albumin and plasma.
The binding of the 3 estradiol-17beta sulfates in solutions of human serum albumin (HSA) and in plasma has been studied by the method of centrifugal ultrafiltration. HSA has one binding site for the 17-sulfate with association constants of about 10(5) to 10(6)M-1 at either 4 degrees or 37 degrees and several sites with association constants of 10(3) to 10(4) M-1. HSA has 3 groups of binding sites for estradiol-17beta disulfate, one binding site with association constants of about 10(6) M-1 at either 4 C or 37 C, about 2 binding sites with association constants of about 10(4)M-1 and several sites with association constants of about 10(3)M-1. The binding data of the 3-sulfate of estradiol-17beta are best interpreted by the postulate of the existence of a tetramer in addition to the monomer of the sulfate in solution. With this postulate, HSA has one binding site with an association constant of about 5-10(5)M-1 and seven binding sites with association constants of about 10(3)M-1 at either 4 C or 37 C. More than 99% of the 17-sulfate or the disulfate of estradiol-17beta is bound in plasma at 37 degrees, with all of the binding accounted for by HSA. The estradiol-17beta sulfates compete with one another for binding to HSA. Strong displacement has also been found by androgen sulfates and, less, by estrogen glucosiduronates.
D000328:Adult; D001665:Binding Sites; D004958:Estradiol / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008956:Models, Chemical; D010949:Plasma / Q000378:metabolism*; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*
D012709:Serum Albumin; D004958:Estradiol