Studies on phospholipid biosynthesis in hepatocytes from alcoholic rats by using radiolabeled exogenous precursors.
We have studied the synthesis of phospholipids in hepatocytes isolated from chronically ethanol-treated rats by using isotopically labelled serine, ethanolamine, and choline as exogenous precursors. Our results demonstrate that ethanol induces specific effects on the biosynthesis of phosphatidylethanolamine and phosphatidylcholine via CDP-derivatives and also on the synthesis of phosphatidylserine via the Ca(++)-dependent base-exchange reaction. Thus, the synthesis of phosphatidylethanolamine from [3-H]ethanolamine and the incorporation of [3H]serine into phosphatidylserine were clearly higher in hepatocytes from ethanol-treated rats compared to controls. The synthesis of phosphatidylcholine from [methyl-14C]choline, on the other hand, decreased markedly, suggesting a specific inhibition of cholinephosphotransferase activity. We have also demonstrated that the phosphatidylcholine levels are markedly decreased in hepatocytes isolated from chronically ethanol-treated rats as a consequence of the lower phosphatidylcholine biosynthesis. The decrease in the incorporation of radioactivity from choline to betaine, which we also found, is interpreted as being the result of a higher use of betaine as methyl donor instead of methionine to maintain the hepatic S-adenosylmethionine levels in chronic alcoholism.
Carrasco
M P
MP
Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of Granada, Spain.
Sanchez-Amate
M C
MC
Segovia
J L
JL
Marco
C
C
D000437:Alcoholism / Q000378:metabolism*; D000818:Animals; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism*; D002798:Diacylglycerol Cholinephosphotransferase / Q000037:antagonists & inhibitors / Q000378:metabolism; D019856:Ethanolamine; D004983:Ethanolamines / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D010713:Phosphatidylcholines / Q000096:biosynthesis; D010714:Phosphatidylethanolamines / Q000096:biosynthesis; D010718:Phosphatidylserines / Q000096:biosynthesis; D010743:Phospholipids / Q000096:biosynthesis*; D011865:Radioisotope Dilution Technique; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012694:Serine / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D004983:Ethanolamines; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D010743:Phospholipids; D014316:Tritium; D012694:Serine; D019856:Ethanolamine; D002798:Diacylglycerol Cholinephosphotransferase; D002794:Choline