Ribonucleic acid synthesis in regenerating and embryonic liver: II. The synthesis of RNA during embryonic liver development and its relationship to regenerating liver

Abstract

The synthesis of RNA in fetal liver has been examined from the 14th day until parturition. Populations of RNA molecules present at various stages were intercompared by competition in DNA/RNA hybridization reactions. Evidence is presented for the synthesis of characteristic molecules of RNA at different stages in the development of fetal liver. The greatest apparent diversity in the RNA molecules synthesized and the most distinctive population occur at 14 days of fetal development, the earliest time studied. Since some RNA molecules actively synthesized at one time are absent one day later, much of the RNA made must be of limited life-time. As fetal liver development proceeds, the RNA becomes more similar to that of the adult, although some molecules present in adult liver are absent in early embryonic liver. The new species of RNA which appear prior to regeneration in response to partial hepatcetomy were compared with those associated with rapid cell proliferation in embryonic liver. Since 14-day embryonic liver RNA is an efficient competitor for early regenerating liver RNA, much of the characteristic regenerating liver RNA appears to be the result of re-activation of genes active in liver development but repressed in adult liver.