Passage of heterologous serum proteins from mother into fetal compartments in the rabbit

¹ Department of Zoology, University of California, Los Angeles, California

Dutch rabbits were injected with human or bovine serum albumin or human gamma globulin at 19, 24, and 28 days of gestation. Fetal serum, stomach contents, and exocoel, amniotic, and allantoic fluids were collected at intervals from 1 to 48 hr later and titrated with specific antisera. The presence of injected protein in fetal samples was confirmed by electrophoresis and absorption of rabbit protein, followed by the precipitin test. The three nonantibody proteins were detected in fetal serum and exocoel fluid after day 19 and in all fetal compartments after day 22, as soon as 1 hr after injection into the mother and after a maternal dose as low as 10 mg/kg., About 1 mg was found in the entire fetus 24 hr after a maternal dose of 62.5 mg/kg. The proteins passed from maternal circulation to uterine lumen, to exocoel, to allantois and amnion, and from amnion to stomach. They passed from mother to fetal circulation via the vessels of the yolk sac splanchnopleure and not through the allantoidean placenta.