Changes of nuclear membrane fluidity during rat liver regeneration.

We have previously shown that the nuclear membrane fluidity is affected by lipid composition changes and that is very high, particularly in the hydrophobic core. The aim of this work is to study the modifications of nuclear membrane fluidity in relation to the cell cycle. Since compensatory hepatic growth is an informative and well characterised model for natural cell proliferation, the nuclear membrane fluidity, detected by two fluorescent probes, was studied at various regenerating times, ranging from 0 to 30 hours after partial hepatectomy. At 18 hours after partial hepatectomy the nuclear membrane fluidity increased and at 30 hours the higher values of hydrophobic core fluidity were observed. The behaviour of fluidity was related to the nuclear membrane neutral-sphingomyelinase activity and, then, to the content of sphingomyelin. Therefore, the significant changes of the nuclear membrane fluidity and of the neutral-sphingomyelinase activity found during rat liver regeneration suggested a their likely role in signal transduction pathways implying cell regeneration.