Choline incorporation into phospholipids in mesothelial cells in vitro.
OBJECTIVE
To determine the effect of extracellular choline concentration on phospholipid production and handling by peritoneal mesothelial cells in vitro.


METHODS
Radiolabeled choline was used to monitor the formation of phosphatidylcholine (PC), sphingomyelin (SPH), and lysophosphatidylcholine (LPC) by rat and rabbit mesothelial cells as a function of concentration and time of exposure to choline. The subcellular location of the newly formed phospholipids was examined by ultracentrifugation in Percoll-sucrose gradients using analytical cell fractionation techniques. The fatty acid composition of the PC formed was determined by thin-layer chromatography (TLC) and gas chromatography.


RESULTS
Choline incorporation into PC, SPH, and LPC increased with extracellular choline levels up to 640 mumol/L, which is 100 times greater than physiological levels of choline in plasma and 20 times higher than choline levels measured in peritoneal dialysis effluent. The newly formed, radiolabeled phospholipids were primarily found in a single subcellular compartment that exhibited a buoyant density of 1.05 g/mL in Percoll-sucrose gradients. Analysis of the fatty acyl groups of PC obtained from the mesothelial cells showed enrichment in palmitic [16:0], oleic [18:1], and linoleic [18:2] acids.


CONCLUSIONS
The rate of phospholipid formation by mesothelial cells in vitro can be manipulated, in part, by choline concentration.
Hjelle
J T
JT
Department of Basic Sciences, University of Illinois College of Medicine at Peoria 61656.
Steidley
K R
KR
Pavlina
T M
TM
Dobbie
J W
JW
D000818:Animals; D002250:Carbon Radioisotopes; D002458:Cell Fractionation; D002469:Cell Separation; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism* / Q000493:pharmacokinetics; D004847:Epithelial Cells; D004848:Epithelium / Q000737:chemistry / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis; D008244:Lysophosphatidylcholines / Q000032:analysis / Q000096:biosynthesis; D051379:Mice; D010537:Peritoneum / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000032:analysis / Q000096:biosynthesis; D010743:Phospholipids / Q000032:analysis / Q000096:biosynthesis*; D011817:Rabbits; D051381:Rats; D013109:Sphingomyelins / Q000032:analysis / Q000096:biosynthesis; D014316:Tritium
D002250:Carbon Radioisotopes; D005227:Fatty Acids; D008244:Lysophosphatidylcholines; D010713:Phosphatidylcholines; D010743:Phospholipids; D013109:Sphingomyelins; D014316:Tritium; D002794:Choline