The presence and the role of chromatin cholesterol in rat liver regeneration.
OBJECTIVE
It has been shown that cholesterol is necessary in early G1 phase during cell duplication. In the present research we have studied the presence of cholesterol in the hepatocyte chromatin lipid fraction and its behaviour in liver regeneration.


METHODS
Hepatocyte nuclei and chromatin were isolated from normal and regenerating rat liver. The lipid fraction was extracted and analysed by chromatography. The activity of sphingomyelin-synthase in the chromatin was evaluated using labelled phosphatidylcholine.


RESULTS
In the chromatin, the amount of cholesterol is similar to that of sphingomyelin, and it increases in chromatin digested with exogenous sphingomyelinase or proteinase K. It may be concluded that a complex, formed by cholesterol, sphingomyelin and proteins, is present in the chromatin. The particular affinity between sphingomyelin and cholesterol in chromatin with respect the nuclear membrane may be tentatively explained as due to the enrichment in saturated fatty-acids of the chromatin sphingomyelin. Moreover the cholesterol inhibits the chromatin sphingomyelin-synthase activity. During liver regeneration, an increase in chromatin cholesterol is observed between 6 and 18 h after hepatectomy, when the neutral-sphingomyelinase activity increases and the sphingomyelin-synthase is inhibited.


CONCLUSIONS
The cholesterol is present in the chromatin and its amount changes in relation to cell proliferation in regenerating liver.
Albi
Elisabetta
E
Department of Biochemical Sciences and Molecular Biotechnology, Physiopathology, Policlinico Monteluce, 06100, Perugia, Italy.
Magni
Mariapia Viola
MV
D000818:Animals; D002455:Cell Division / Q000502:physiology; D002467:Cell Nucleus / Q000201:enzymology; D002784:Cholesterol / Q000378:metabolism*; D002843:Chromatin / Q000201:enzymology*; D019286:Endopeptidase K / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013108:Sphingomyelin Phosphodiesterase / Q000494:pharmacology; D013109:Sphingomyelins / Q000378:metabolism; D017855:Transferases (Other Substituted Phosphate Groups) / Q000378:metabolism
D002843:Chromatin; D005227:Fatty Acids; D013109:Sphingomyelins; D002784:Cholesterol; D017855:Transferases (Other Substituted Phosphate Groups); C070186:phosphatidylcholine-ceramide phosphocholine transferase; D013108:Sphingomyelin Phosphodiesterase; D019286:Endopeptidase K