Assessment of phospholipid deacylation-reacylation cycles by a stable isotope technique

Incorporation of 18O into glycerophospholipids was determined after incubating mouse peritoneal exudate cells for 1 or 2 h in media containing 40% H(2)18O. Gas chromatography-mass spectrometry of hydrogenated fatty acid methyl esters showed highest amounts of 18O in choline phospholipids and phosphatidylinositol. Acyl groups generally present at the sn-1 position contained at least as much carbonyl 18O as those at the sn-2 position. Considering the route of 18O incorporation via free fatty acid derived through ester hydrolysis in H(2)18O, acyl turnover in certain peritoneal exudate cell phospholipids may equal or exceed 20% per h.