Effects of estrogens on serum lipids and apoproteins of the chicken embryo

Abstract

1. 1. Fertile chicken eggs were injected with 0.25 mg estrone at 9, 10, 12, 14 and 17 days of incubation. Serums from the embryos were assayed 4 days later in each case for total lipids, total non-lipid materials, apoprotein A-I (Apo A-I), apoprotein B (Apo B), phosvitin and lipovitellin. 2. 2. Increases in serum total lipids and serum Apo B were seen at all embryonic stages by 4 days following estrone injection, including the earliest time of injection (9 days of incubation). 3. 3. The ratio of Apo B to total serum lipid (as induced by estrogen treatment) increased as a function of increasing developmental stage. 4. 4. Serum Apo A-I decreased slightly, as a result of estrone injection, during later stages of development. 5. 5. Serum phosvitin (a phosphoprotein subcomponent of vitellogenin, a protein which is specifically induced in adult egg-laying vertebrates by estrogens) was detected by double immunodiffusion at the earliest bleeding (13 days of incubation). However, it was not present in amounts detectable by chemical means until 16 days of incubation. 6. 6. Although the responses were highly variable, the amounts of phosvitin appearing in the serum after estrogen treatment increased as a function of developmental stage. 7. 7. Serum lipovitellin (another subcomponent of vitellogenin) was also detected by double immunodiffusion at the earliest bleeding (13 days of incubation). Although quantitative tests were not carried out on this very dense lipoprotein, immunodiffusion lines show substantial increases in thickness at 16 and 18 days of incubation. 8. 8. No changes in weights of livers (and hence, in rates of cell division therein) were detected.