Estradiol-induced vitellogenin synthesis in duck liver

We have studied the induction of vitellogenin by estradiol in duck liver. From the accumulation of vitellogenin in blood plasma we calculated that the rate of vitellogenin synthesis increases linearly with time for about 4 days after estradiol administration. Vitellogenin from chicken and duck cross-react immunologically and their mRNAs show only 7% sequence divergence. We could therefore determine vitellogenin mRNA content of duck liver using chicken vitellogenin cDNA as a hybridization probe. The number of vitellogenin mRNA molecules per hepatocyte increases from less than one in normal duck liver to 18 000 at 4 days after estradiol injection. The rate of vitellogenin synthesis in vivo is roughly proportional to vitellogenin mRNA content, although the data suggest a somewhat enhanced translation of vitellogenin mRNA at later times after hormone administration. Vitellogenin mRNA levels had returned to control values after 4 weeks after hormone administration. In the first 11 h after secondary administration of hormone vitellogenin mRNA accumulates at an only slightly higher rate than is observed after primary hormonal stimulation.