Induced Formation of Phosphoprotein in Tissues of Cockerels in Vivo and in Vitro.

The appearance of phosphoprotein in the plasma of male birds treated with estrogen has been reported by other investigators (1, 2). Earlier studies from this laboratory have indicated that this process reflects synthesis de novo of a protein fraction normally absent in cockerels and that the initial action of the hormone requires an intact ribonucleic acid-synthesizing system (3). In the present study of the mechanism of this phenomenon, attempts were made to identify the organ responsible for the induced synthesis of these proteins. However, administration of diethylstilbestrol did not appear to cause a detectable increase in the incorporation of radioactive phosphorus in viva into any of the tissues studied. This observation suggested that the secretion of phosphoproteins into the blood stream may be so rapid that their concentration in the appropriate organs remains low at any time. The present results obtained with tissue slices indicate that livers of cockerels which have been treated with diethylstilbestrol in viva can synthesize a phosphoprotein fraction. The identification of phosvitin by paper electrophoresis of unfractioned material is applicable to egg yolk (4) but not to plasma, where phosphoproteins are more extensively complexed with lipoproteins, lipids, and Ca2f ions (5). Therefore, only after the elaboration of a suitable fractionation procedure was the phosphoprotein in the plasma of laying hens identified, by Heald and McLachlan (6), as phosvitin. The plasma of cockerels after treatment with estrogen, as well as the soluble fraction of incubated liver slices from such animals, has now been subjected to a similar procedure for liberating the material from the complex. Column chromatography and electrophoresis of the resulting preparation showed that the phosphoprotein produced by liver slices, or present in the plasma of estrogen-treated cockerels, or in the plasma of laying hens, is identical.