Investigations were made to clarify the physiological function of α-embryonic protein (αEP) in the fowl, the fluctuation of its level in the sera of embryos and chicks, and the immunological relation between αEP in the sera and egg proteins.
About 600 embryos and 300 chicks from White Leghorns, Rhode Island Reds and their reciprocal crosses and Hinaidoris were employed. The levels of αEP were measured using a single radial immunodiffusion method. The following results were obtained:
1. A common antigen for αEP in the chicken sera was observed in yolk of 20-day-old embryos and fresh egg white, but was not in human fetal sera.
2. The level of αEP in the sera increased gradually with the development of embryos from the 8th day of incubation, and reached the highest value (70-90mg/dl) in 16-day-old embryos. Thereafter, its level decreased gradually and showed 11-19mg/dl at hatching time, and almost disappeared in 7-day-old chicks. It was found that fluctuations of αEP levels in the sera of embryos and chicks showed a similar curve to changes of their yolk sac weights, and there were no significant in αEP levels among these breeds or crosses.
3. The highest value (about 4%) in the ratio of αEP level to total protein level in the sera was observed in 16-day- or 19-day-old embryos, and the ratio decreased thereafter. But in Hinaidoris two peaks of high levels were present at the 14 and 19 days of incubation.
4. No significant correlation was recognized between αEP levels and body weight, or total serum protein levels in embryos or chicks.