title: Mechanism of the enrichment of phosphatidylcholine in liver accompanying enzyme induction by phenobarbital.
abstract: The mechanism of the increase of phosphatidylcholine in liver, accompanying enzyme induction by phenobarbital, has been studied in rats. Using radioactively labeled precursors, the two main pathways of phosphatidylcholine biosynthesis--the CDP-choline pathway and the methylation of phosphatidylethanolamine--were analyzed after pretreatment with 4 doses of phenobarbital (80 mg/kg) on 3 consecutive days. After i.v. injection of choline [Me-3H], choline [Me-14C] or NaH2[32P]O4 the specific radioactivity (sp. act.) of phosphatidylcholine (dpm/nmol) was decreased by 60%, and after methionine [Me-3H] or ethanolamine [1.2-14C] by 40% compared to control rats. These changes are partly due to the increased concentration of phosphatidylcholine and phosphatidylethanolamine, causing the incorporated precursors to dilute, and partly to a secondary effect which leads to a reduction of the sp. act. of free choline in pretreated animals. The concentration of glycerylphosphorylcholine, one of the metabolites of phosphatidylcholine catabolism, was also diminished by almost 50%. From these results it may be concluded that the increase of phosphatidylcholine is due to a retardation of its breakdown rather than to an increase of its synthesis.
mesh_terms: D000818:Animals; D002794:Choline / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects*; D004983:Ethanolamines / Q000378:metabolism; D050356:Lipid Metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology*; D010710:Phosphates / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013997:Time Factors
chemical_list: D004983:Ethanolamines; D010710:Phosphates; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010761:Phosphorus Radioisotopes; D011506:Proteins; D008715:Methionine; D002794:Choline; D010634:Phenobarbital