[Nuclear pore density in rat liver cells during regeneration and x-ray irradiation of the animals].

Cytoplasmic as well as nucleoplasmic surfaces of the pore complexes (PC) could be observed using freeze-etching method. The density of PCs per 1 micron2 of nuclear envelope (NE) surface in regenerating liver (9.9) is twice as that in resting liver (5.3). 1 hour after 1200 R X-ray irradiation the pore density in regenerating liver decreases 5.8-fold, consisting only of 1.7 PCs per 1 micron2 of the NE. The structure of the PC after irradiation undergoes degradation and normal PCs practically disappear; only their "ghosts" remain. Peripheral and possibly central granules of the PC appear to consist of some subunits with their diameter of 4--5 nm. The central granule forms a channel through which RNA containing material may be transported from the nucleus to the cytoplasm. The non-uniform state of the PC, observed on platinum-carbon replicas of cleaved nuclei, and the non-altered PC associate with the dense lamina of the NE, after detergent treatment of isolated nuclei indicate that the PC could be formed inside the nuclei and to be "inserted" into the NE membranes in the course of their processing.