title: The metabolism of the phosphonium analogue of choline in vitro and in vivo, and its detection in phospholipids by 31P-NMR.
abstract: 1. The phosphonium analogues of choline, phosphorylcholine, CDPcholine and phosphatidylcholine were synthesized chemically and characterized by 1H-NMR and 31P-NMR; in 1,2-distearoyl-DL-glycero-3-phosphorylphosphocholine, the 31P-NMR chemical shift of phosphonium relative to phosphate was--28.2 ppm. 2. A comparison was made of the rates of reaction of choline kinase, cholinephosphate cytidyltransferase, cholinephosphotransferase and phospholipase C on natural and phosphonium substrates. Enzyme reaction rates were similar for all but the cytidyltransferase, which exhibited a 3-fold preference for the normal substrate. 3. Weanling rats were maintained for 6 weeks on a diet in which choline was fully replaced by phospho[1,2-14C2]choline mixed with a trace of [Me-3H] choline. Incorporation of phosphocholine into liver lipids was detectable by 31P-NMR even in crude tissue homogenates. Choline-based phospholipids of liver, kidney, lung and brain were extracted, and phosphocholine incorporation calculated from 31P-NMR peak area ratios. The phosphatidylcholine analogues were separated by preparative thin-layer chromatography. Incorporation of phosphocholine ranged from 33% in lung phosphatidylcholine to 6% in kidney sphingomyelin. Variations in 14C/3H ratio between feed and phospholipid extracts indicated preferences for exogenous choline over phosphocholine varying from 1.3: 1 in brain to 3.2: 1 in liver. The results indicated that phosphocholine is a potentially useful 31P-NMR probe for the study of membrane lipids.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002794:Choline / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009928:Organ Specificity; D063065:Organophosphonates / Q000378:metabolism*; D010743:Phospholipids / Q000096:biosynthesis*; D051381:Rats
chemical_list: D063065:Organophosphonates; D010743:Phospholipids; D002794:Choline