title: Essential fatty acid metabolism in cultured human airway epithelial cells.
abstract: To characterize essential fatty acid metabolism of human airway epithelium, we examined the capacity of epithelial cells to incorporate and desaturate/elongate 18:2(n - 6) and the turnover of phospholipid fatty acyl chains in these cells. Epithelial cells were cultured for 5-7 days and incubated with [1-14C]18:2(n - 6) (1 microCi, 100 nmol). The essential fatty acid profile of the cells was readily modified by 18:2(n - 6) supplementation to culture medium. After 4 h incubation, 32 +/- 5.6 nmol of [1-14C]18:2(n - 6) was incorporated into phospholipids (65 +/- 9.5%, of which 74% was incorporated into phosphatidylcholine (PC)) and neutral lipid (31 +/- 10%) per mg protein of cultured cells. 30 +/- 8% of [1-14C]18:2(n - 6) incorporated, was converted to homologous trienes, tetraenes and pentaenes, the major products being 20:3(n - 6) and 20:4(n - 6). The conversion of 18:2(n - 6) was time-dependent and donor age-related. A higher proportion of 20:3(n - 6) and 20:4(n - 6) was incorporated into phosphatidylinositol (PI) and phosphatidylethanolamine (PE). About 10-15% of total products formed from 18:2(n - 6) was released from membrane to culture medium. Both 20:4(n - 6) and 20:5(n - 3) inhibited 18:2(n - 6) incorporation and desaturation. Rate of incorporation of 18:2(n - 6) was more than either 18:1(n - 9) or 16:0. With pulse-chase studies, the half-life of 18:2(n - 6) in PC, PI and PE was estimated to be 5.5, 6.0 and 7.3 h, respectively. These data indicate active metabolism of essential fatty acids in human airway epithelial cells. This metabolism may play a key role in the regulation of membrane properties and function in these cells.
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Canada.
authors.forename: J X
authors.initials: JX
authors.lastname: Kang
authors.forename: S F
authors.initials: SF
authors.lastname: Man
authors.forename: N E
authors.initials: NE
authors.lastname: Brown
authors.forename: P A
authors.initials: PA
authors.lastname: Labrecque
authors.forename: M L
authors.initials: ML
authors.lastname: Garg
authors.forename: M T
authors.initials: MT
authors.lastname: Clandinin
mesh_terms: D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D004848:Epithelium / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005228:Fatty Acids, Essential / Q000378:metabolism*; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D006801:Humans; D050602:Linoleoyl-CoA Desaturase; D010743:Phospholipids / Q000302:isolation & purification / Q000378:metabolism; D014280:Triglycerides / Q000302:isolation & purification; D014420:Turbinates / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D005228:Fatty Acids, Essential; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D010743:Phospholipids; D014280:Triglycerides; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase