Cytophotometric determination of nuclear non-histone protein in the pre-replicative phase of rat liver regeneration

Nuclear non-histone protein (NHP) and cytoplasmic protein was determined cytophotometrically in Feulgen-Naphthol Yellow S (NYS) stained, isolated parenchymal liver cells during the first 16 h following partial hepatectomy in rats. Nuclear NYS binding was also measured in histological sections, and the RNA polymerase activity of parenchymal nuclei was assayed autoradiographically. The following results were obtained: 1. 1. From 4 h on, the mean nuclear NHP in regenerating livers is significantly higher than in sham-operated controls; at 16 h the difference is 33%. 2. 2. The frequency distributions of nuclear NHP suggest that the increase in mean nuclear NHP is due to the gradual emergence of cells that have higher nuclear NHP values than any cells in the sham-operated controls. The number of such cells amount to a third of the population at 12 and 16 h after the partial hepatectomy. 3. 3. The measurements of nuclear NYS binding on histological sections show that the cells with high nuclear NHP values at 12 and 16 h after partial hepatectomy are predominantly located to the periportal area. 4. 4. The mean RNA polymerase activity and the mean cytoplasmic protein content also increase after partial hepatectomy, and the highest values of both parameters were found in cells with high nuclear NHP values.