title: Binding of 5 alpha-dihydroprogesterone to proteins in human pregnancy serum.
abstract: The binding of 5 alpha-dihydroprogesterone (DHP) to proteins in pregnancy serum has been investigated and compared with the binding of progesterone. Characteristic properties of the DHP-serum protein interaction were unsaturability, low affinity and poor complex stability. Fractionation of serum using a variety of protein separation techniques, revealed that DHP interacts with several proteins. At low temperature (0--4 degrees C) albumin appeared to be the principal binding component whereas higher temperatures seemed to favour binding to beta-lipoproteins and alpha 2-macroglobulin. Binding to specific binding proteins such as the corticosteroid binding globulin (CBG) and the sex hormone-binding globulin, (SHBG) were detectable but appeared to be quantitatively unimportant. Progesterone showed a similar multicomponent interaction but differed from DHP in the extent of binding to CBG. Binding of either hormone to the alpha 1-acid-glycoprotein was negligible. The present study shows that the high endogenous DHP levels present in pregnancy sera are caused by factors other than high affinity protein binding.
mesh_terms: D043582:5-alpha-Dihydroprogesterone; D001798:Blood Proteins / Q000378:metabolism*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D007525:Isoelectric Focusing; D008077:Lipoproteins, LDL / Q000097:blood; D009961:Orosomucoid / Q000097:blood; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000097:blood*; D011277:Pregnanediones / Q000097:blood*; D011374:Progesterone / Q000097:blood; D011485:Protein Binding; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D014156:Transcortin / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000097:blood
chemical_list: D001798:Blood Proteins; D008077:Lipoproteins, LDL; D009961:Orosomucoid; D011257:Pregnancy Proteins; D011277:Pregnanediones; D012738:Sex Hormone-Binding Globulin; D000511:alpha-Macroglobulins; D011374:Progesterone; D014156:Transcortin; D043582:5-alpha-Dihydroprogesterone