Nuclear phospholipids during the adaptation of human EUE cells to hypertonic stress

The phospholipid component of interphase nuclei was analysed in EUE cells (an established cell line from embryonic human epithelium) grown in an isotonic culture medium and during the adaptation process to a hypertonic medium, using a highly specific ultracytochemical procedure, viz. labelling with the phospholipase A2 gold-complex. Within the nucleus, the phospholipids were localized in domains involved in different steps of the synthesis and processing of the RNA. These localizations did not vary at the two key steps of the adaptation process to hypertonic medium: short-term treatment (6 h) representing critical shock condition, and long-term growth (5 days) representing the adapted cells under survival conditions. On the contrary, deep changes of the labelling intensity of phospholipids at these sites occurred at the different times of hypertonic treatment and followed the same course as those observed in the ultramorphological patterns of transcription: the chromatin condensation, as evaluated by image analysis, the permanent nucleolar components, the interchromatin and the perichromatin granules. These data endorse the hypothesis that nuclear phospholipids could be involved in different steps of the transcriptional activity. They are indicative of the deep changes occurring in the EUE cells submitted to hypertonic stress.