ORGAN-SPECIFIC ESTROGEN-INDUCED RNA SYNTHESIS RESOLVED BY DNA-RNA HYBRIDIZATION IN THE DOMESTIC FOWL^*

Abstract

In the domestic fowl and other oviparous vertebrates, estrogens induce hepatic synthesis of yolk proteins. The oviduct also increases in size and produces ovalbumin when estrogens are administered. DNA-RNA hybridization assays indicate that within 105 minutes following treatment with estrone the liver of immature pullets contains most, if not all, of the liver RNA species that are present in the livers of the laying hen. Because of limitations of the nucleic acid hybridization technique, which remain to be clearly defined, it is not known whether the hepatic RNA populations in estrone-treated pullets and laying hens are completely homologous or differ in some important way. The results indicate that the genomic response in the avian liver to exogenous estrone is „normal” (relative to the laying hen) and further suggest that the hepatic response to estrogen is primarily pertinent to vitellinogenesis.

DNA-RNA hybridization assays on total RNA also indicate that estrogen-induced RNA species in the liver are not homologous to estrogen-evoked RNA species of the oviduct. Therefore, in these two target organs estrogen-evoked RNA synthesis appears to be in part organ-specific. These data indicate that the specificity of hormone action can be explained in part on the basis of induced synthesis of specific RNA molecules. Whether these alterations in transcription are due to indirect hormonal action or are the result of a primary action of estrogens or estrogen-binding site complexes on the genome and/or its repressors remains a basic question.