title: Molecular and structural composition of phospholipid membranes in livers of marine and freshwater fish in relation to temperature.
abstract: The compositions and physical states of the liver phospholipids of marine and freshwater fish adapted to relatively constant but radically different temperatures were investigated. Fish adapted to low temperature (5-10 degrees C) accumulated more unsaturated fatty acids than those in a warm (25-27 degrees C) environment. There were no measurable differences in the gross fatty acid compositions of the total liver phospholipids from identical thermal environments. Docosahexaenoic acid (22:6) did not seem to participate in the process of adaptation. Cold adaptation was coincidental with oleic acid (18:1) accumulation, preferentially in the phosphatidylethanolamine. Determination of the molecular species composition of phosphatidylethanolamine revealed a 2- to 3-fold and 10-fold increase in the level of 18:1/22:6 and 18:1/20:5 species, respectively. ESR spectroscopy revealed a 7-10% compensation in the ordering state of native phospholipids with temperature. Combination of 16:0/22:6 phosphatidylcholine with phosphatidylethanolamines of cold-adapted marine fish showed a drastic fluidization near the C-2 segment of the bilayer, but not in the deeper regions. An appropriate combination (75:25) of phosphatidylcholines from warmth-adapted marine fish with phosphatidylethanolamines from cold-adapted marine fish mimicked a 100% adaptational efficacy in the C-2 segment as compared with the phosphatidylethanolamines of warmth-adapted marine fish. A specific role of 18:1/22:6 phosphatidylethanolamine in controlling membrane structure and physical state with thermal adaptation is proposed.
authors.affiliation: Institute of Biochemistry, Hungarian Academy of Sciences, Szeged.
authors.forename: I
authors.initials: I
authors.lastname: Dey
authors.forename: C
authors.initials: C
authors.lastname: Buda
authors.forename: T
authors.initials: T
authors.lastname: Wiik
authors.forename: J E
authors.initials: JE
authors.lastname: Halver
authors.forename: T
authors.initials: T
authors.lastname: Farkas
mesh_terms: D000064:Acclimatization; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis; D005399:Fishes / Q000502:physiology*; D005454:Fluorescence Polarization; D005583:Fourier Analysis; D008099:Liver / Q000737:chemistry / Q000378:metabolism*; D008563:Membrane Lipids / Q000032:analysis / Q000378:metabolism*; D010743:Phospholipids / Q000032:analysis / Q000378:metabolism*; D013045:Species Specificity; D013055:Spectrophotometry, Infrared; D013696:Temperature
chemical_list: D005227:Fatty Acids; D008563:Membrane Lipids; D010743:Phospholipids