Re-evaluation of the presence of multiple haemoglobins during the ontogenesis of the chicken

Haemolysates of red blood cells from embryos of several developmental stages ranging from 2 to 21 incubation days and from post-hatching chickens of various age groups were analysed by ion-exchange chromatography, agarand starch-gel electrophoresis, immunoelectrophoresis with specific antisera and polypeptide chain electrophoresis. With these methods two adult (Ax and A2) and six embryonic (Ej-Eg) haemoglobin types were identified. Antisera specific for the major adult haemoglobins (Ax and A2) as well as antisera specific for the major embryonic haemoglobins (E3, E4) could be prepared. Throughout embryogenesis the haemoglobin types contribute in varying amounts to the total haemoglobin pattern. Three periods of haemoglobin synthesis could be recognized, the transition between these periods occurred at the 6th and 12th incubation day. The first period is characterized by the presence of two major embryonic haemoglobins (E3 and E4) and two minor embryonic haemoglobins (E2 and E5). During the second period E3 and E4 are largely replaced by a major adult haemoglobin (A2) and a new embryonic haemoglobin (Ex). The third period is characterized by the appearance of a second adult haemoglobin (Ax) and a new minor embryonic haemoglobin (E6) with a concomitant decrease of E2 and E5. At the time of hatching two embryonic haemoglobins (Ex and E6) are still present. Besides Ax and A2, several minor haemoglobin fractions were inconsistently found in adult chickens. Evidence has been obtained that these additional fractions are reflecting a so called minor heterogeneity or separation artifacts. The haemoglobins Al5 A2 and Ej-E6 show different polypeptide chain compositions. Three embryo-specific chains could be demonstrated (/? E2E5,yE4 and #E3). The production of the polypeptide chains appears to be correlated with the aforementioned periods of haemoglobin synthesis. The genetic and morphological implications of the findings are discussed.