Induction of Phosvitin by Oestradiol in Rooster Liver needs DNA Synthesis

THE synthesis of an egg yolk protein phosvitin, which is normally synthesized by the laying hen, can be induced in immature pullets1 or roosters2 by treatment with oestrogens. Phosvitin appears in the plasma of roosters with a lag period of 24 h after a single injection of oestradiol, reaching maximum values at 72 h3. The lag period is reduced on sequential injections of the hormone. The peak values of the protein in plasma as well as total amounts synthesized are enhanced progressively with successive exposures to the hormone3. The livers of hormone-treated birds become larger4,5. These observations suggested that the amplified response to sequential injections of the hormone could be due to more cells that synthesize the protein being mobilized. Our experiments suggest that DNA synthesis is necessary before the target cells can be stimulated to synthesize phosvitin by oestrogens.