title: Mechanisms of accumulation of arachidonate in phosphatidylinositol in yellowtail. A comparative study of acylation systems of phospholipids in rat and the fish species Seriola quinqueradiata.
abstract: It is known that phosphatidylinositol (PtdIns) contains abundant arachidonate and is composed mainly of 1-stearoyl-2-arachidonoyl species in mammals. We investigated if this characteristic of PtdIns applies to the PtdIns from yellowtail (Seriola quinqueradiata), a marine fish. In common with phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn) and phosphatidylserine (PtdSer) from brain, heart, liver, spleen, kidney and ovary, the predominant polyunsaturated fatty acid was docosahexaenoic acid, and levels of arachidonic acid were less than 4.5% (PtdCho), 7.5% (PtdEtn) and 3.0% (PtdSer) in these tissues. In striking contrast, arachidonic acid made up 17.6%, 31.8%, 27.8%, 26.1%, 25.4% and 33.5% of the fatty acid composition of PtdIns from brain, heart, liver, spleen, kidney and ovary, respectively. The most abundant molecular species of PtdIns in all these tissues was 1-stearoyl-2-arachidonoyl. Assay of acyltransferase in liver microsomes of yellowtail showed that arachidonic acid was incorporated into PtdIns more effectively than docosahexaenoic acid and that the latter inhibited incorporation of arachidonic acid into PtdCho without inhibiting the utilization of arachidonic acid for PtdIns. This effect of docosahexaenoic acid was not observed in similar experiments using rat liver microsomes and is thought to contribute to the exclusive utilization of arachidonic acid for acylation to PtdIns in yellowtail. Inositolphospholipids and their hydrolysates are known to act as signaling molecules in cells. The conserved hydrophobic structure of PtdIns (the 1-stearoyl-2-arachidonoyl moiety) may have physiological significance not only in mammals but also in fish.
authors.affiliation: Department of Applied Biological Science, Fukuyama University, Japan. tamot@fubac.fukuyama-u.ac.jp
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Dai
authors.initials: D
authors.lastname: Iwawaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Yoshimichi
authors.initials: Y
authors.lastname: Takai
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Morishige
authors.forename: Kaoru
authors.initials: K
authors.lastname: Murakami
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Satouchi
mesh_terms: D000215:Acylation; D000818:Animals; D016718:Arachidonic Acid / Q000032:analysis / Q000378:metabolism*; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D004281:Docosahexaenoic Acids / Q000032:analysis; D005227:Fatty Acids / Q000032:analysis; D005260:Female; D005399:Fishes; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism; D009928:Organ Specificity; D010053:Ovary / Q000737:chemistry / Q000378:metabolism; D010716:Phosphatidylinositols / Q000737:chemistry / Q000378:metabolism*; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D013154:Spleen / Q000737:chemistry / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D010716:Phosphatidylinositols; D010743:Phospholipids; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid