Mechanisms of hepatic phosphatidylcholine synthesis in the developing guinea pig: contributions of acyl remodelling and of N-methylation of phosphatidylethanolamine.
Hepatic phosphatidylcholine (PC) from the immature fetal guinea pig at day 55 of gestation comprised mainly unsaturated molecular species containing C18:2(n-6) and C22:6(n-3) at the sn-2 position, reflecting placental permeability to essential fatty acids. At both day 55 and term (day 68), [Me-14C]choline was incorporated in utero over 3 h largely into sn-1-C16:0 PC species, with incorporation into sn-1-C18:0 PC species increasing by 18 h of incubation. Comparison of specific radioactivities after 3 h and 18 h suggests PC acyl remodelling by phospholipase A1. No incorporation into C20:4(n-6)-containing PC species could be detected of either [Me-14C]choline in vivo or CDP-[Me-14C]choline in isolated microsomes. The major phosphatidylethanolamine (PE) species were 16:0/22:6 and 18:0/22:6. Although [14C]ethanolamine was initially incorporated mainly into sn-1-C16:0 species, specific-radioactivity analysis suggested differential turnover rather than acyl remodelling. [1,2-14C]Ethanolamine and [Me-14C]methionine incorporation into PC molecular species indicated that both newly synthesized and total PE pools were available for N-methylation. Since the PC pool synthesized from PE included C20:4- and C22:6-containing species, N-methylation may provide a mechanism for supplying essential long-chain fatty acids to developing tissues that can be regulated independently from bulk PC synthesis.
Burdge
G C
GC
University of Southampton, U.K.
Kelly
F J
FJ
Postle
A D
AD
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D002794:Choline / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003566:Cytidine Diphosphate Choline / Q000378:metabolism; D019856:Ethanolamine; D004983:Ethanolamines / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D006168:Guinea Pigs; D008099:Liver / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D008745:Methylation; D008862:Microsomes, Liver / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D010714:Phosphatidylethanolamines / Q000378:metabolism*
D004983:Ethanolamines; D005231:Fatty Acids, Unsaturated; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D003566:Cytidine Diphosphate Choline; D019856:Ethanolamine; D008715:Methionine; D002794:Choline