Endocrinology, Vol 117, 1404-1408, Copyright © 1985 by Endocrine Society
Evidence for the direct transfer of corticosteroid-binding globulin from plasma to whey in the guinea pig
EA Kato, BR Hsu, WJ Raymoure and RW Kuhn
Two steroid-binding proteins, corticosteroid-binding globulin (CBG) and
progesterone-binding globulin (PBG), are known to be present in the milk
whey of lactating guinea pigs. After injection of radioiodinated CBG into
the maternal circulation, labeled CBG was found in the milk whey. The
labeled whey CBG was identical to its plasma counterpart on the basis of
size (sucrose gradients, Sephacryl S-200 gel filtration, and sodium dodecyl
sulfate-gel electrophoresis), charge (DEAE- chromatography and
polyacrylamide gel electrophoresis), and immunoprecipitability. In
contrast, radioiodinated ovalbumin was not transferred to the milk. These
results demonstrate that the CBG present in guinea pig whey results from
the direct transfer of CBG from plasma to milk.
