RNA release from isolated brain cell nuclei: influence of the postnatal cerebral development

A method to measure the "in vitro" RNA release from rat brain cell nuclei was described. Nuclear RNA was prelabelled "in vivo" for 30 or 120 min. In the first case the released RNA was heterogeneous and its electrophoretic mobility was similar to that of cytoplasmic messenger RNAs; nuclei prelabelled for 120 min mostly released the two major species of ribosomal RNAs. The release of mRNAs from the nuclei increased during cerebral development while that of the ribosomal RNAs did not. The increased capacity of the nuclei to release "radidly labelled" RNA with age neither determined an increase of the polysomal population, nor seemed to be dependent on cytoplasmic macromolecules.