Modification in nucleocytoplasmic transport of RNA in vitro after whole body X irradiation

Rats were sacrified at different times after injection of ¹⁴C-orotate and liver nuclei were isolated and incubated in a cell-free system made of a soluble cytoplasmic fraction from non-irradiated rat livers. The release of ribonucleoproteins from labelled nuclei to the incubation medium was measured on nuclei from normal and total-body irradiated rats (500 to 2000 R). When using short labelling times in vivo (30 min), which would label predominantly messenger-type RNP, the nuclear transport activity was depressed soon (3 hr) after whole-body irradiation, but increased later (24 hr). When the labelling time in vivo is increased to 2 hr, no significant difference was observed between control and irradiated groups. Transport of the stable ribosomal type Rnp, observed 24 hr after both labelling and irradiation, was depressed. These results are discussed in view of previous personal studies on radiation effects on liver RNA synthesis and polyribosome formation in vivo.