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

Rats were sacrificed at different times after injection of 14C-orotate and liver nuclei were isolated and incubated in a cell-free system made of 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 at early times (3 h) after whole-body irradiation, but increased at later times (24 h). When the labelling time in vivo is increased to 2 h, no significant difference was observed between control and irradiated groups. Transport of the stable ribosomal-type RNP, observed 24 h after both labelling and irradiation, was depressed. These results are discussed in view of previous personal studies on radiation effect on liver RNA synthesis and polyribosomes formation in vivo.