The influence of Triton X-100 on the nuclear envelope of the isolated liver cell nuclei.

In order to obtain more precise information on an eventual presence of extra-membranous lipids in the interior of the nucleus, the effects of Triton X-100 on the lipid content and ultrastructure of isolated rat liver nuclei was investigated. Enzyme markers (a.o. glucose-6-phosphatase) were used to control impurities of the nuclear fractions biochemically along with transmission electron microscopy and qualitative and quantitative light microscopy to check the condition of the nuclei obtained. Treatment of the nuclear fraction with increasing concentrations of Triton X-100 resulted in a decrease of the phospholipid content down to 25% at a Triton X-100/protein ratio of 0.4. A further decrease to 8% was measured at a ratio of 1.5. Electron microscopy of nuclei of the latter group showed nuclei containing outer membrane fragments in 2.5% of their surfaces. The composition of lipids extracted from a nuclear fraction appeared to be markedly changed after treatment with Triton X-100 with an increase of the percentage of neutral lipids and the phospholipids diphosphatidyl-glycerol and spingomyelin. From the chemical and morphological data obtained, the conclusion was drawn that a substantial part of the lipids remaining in the isolated nuclei after treatment with Triton X-100 is localized in both membranes of the nuclear envelope. It cannot however, be excluded that a small portion would be present in the interior of the nuclei.