The Metabolism of Serum Proteins in the Hen and Chick and Secretion of Serum Proteins by the Ovary of the Hen

In the chicken, serum gamma globulin (CGG) is preferentially transferred by the follicular epithelium of the ovary to the developing ova. The concentration of gamma globulin in the yolk of the unfertilized egg is many times the concentration of chicken serum albumin (CSA). This transfer occurs largely during the 4 to 5 days preceding ovulation when the growth of the ovum is most rapid. Thus, in the chicken, the follicular epithelium of the ovary serves the same purpose in the passive immunization of offspring as does the acinar epithelium of the udder in ungulates and the extraembryonic membranes in rabbits and man. The amount of gamma globulin synthesis by the chick is low during the first 2 weeks of life and is associated with low levels of serum gamma globulin. By the end of the 1st month of life, the level of serum gamma globulin increases, presumably reflecting an increased rate of synthesis. In the adult hens the half-life of IlSl-labeled CSA is 66 hours and that of I13Mabeled CGG, 35 hours, while in the newly hatched chick for I181-1abeled CSA it is 42 hours and for PMabeled CGG, 72 hours. Thus, this species shows a gamma globulin sparing in the first days of life, as do most mammalian species. T h e secret ion of serum proteins by the chicken ovary into the developing ova has several interest ing features and consequences. I t provides a useful mode l for s tudying t ranspor t of serum proteins and specific an t i body across an epithelial m e m b r a n e in different stages of deve lopment , since various stages of the developing ova, each su r rounded by the ovar ian follicular ep i the l ium in a cor responding stage of deve lopment , a re present simultaneously in a single laying hen. T h e passage of g a m m a globul in f rom the