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