Steroid-binding proteins in guinea pig milk and plasma.
The levels of two steroid-binding proteins, progesterone-binding globulin (PBG) (1) and corticosteroid-binding globulin (CBG), present in the plasma of pregnant guinea pigs were determined just before and after parturition. Both PBG (3.37 +/- 2.1 microM) and CBG (10.1 +/- 1.7 microM) were present in high levels just before parturition and were found to decrease with a half-life of 2 days after delivery. PBG and CBG were also found in the milk whey of lactating guinea pigs but at much lower levels (26.5 +/- 12 and 375 +/- 18 nM, respectively, on day 1 post partum). The whey content of each protein declined with a half-life of 3 days. The whey steroid-binding proteins were indistinguishable from their plasma counterparts on the basis of ion exchange and gel filtration chromatographies, sucrose gradient centrifugation, susceptibility to heat denaturation, and hormone binding specificity.
D000510:Alpha-Globulins / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D005260:Female; D006168:Guinea Pigs; D006854:Hydrocortisone / Q000378:metabolism; D007700:Kinetics; D008892:Milk / Q000032:analysis*; D011247:Pregnancy; D011270:Pregnancy, Animal; D011374:Progesterone / Q000378:metabolism; D011376:Progesterone-Binding Globulin / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D014156:Transcortin / Q000302:isolation & purification / Q000378:metabolism*
D000510:Alpha-Globulins; D011376:Progesterone-Binding Globulin; D011374:Progesterone; D014156:Transcortin; D006854:Hydrocortisone