title: Sodium pump molecular activity and membrane lipid composition in two disparate ectotherms, and comparison with endotherms.
abstract: Previous research has shown that the lower sodium pump molecular activity observed in tissues of ectotherms compared to endotherms, is largely related to the lower levels of polyunsaturates and higher levels of monounsaturates found in the cell membranes of ectotherms. Marine-based ectotherms, however, have very polyunsaturated membranes, and in the current study, we measured molecular activity and membrane lipid composition in tissues of two disparate ectothermic species, the octopus (Octopus vulgaris) and the bearded dragon lizard (Pogona vitticeps), to determine whether the high level of membrane polyunsaturation generally observed in marine-based ectotherms is associated with an increased sodium pump molecular activity relative to other ectotherms. Phospholipids from all tissues of the octopus were highly polyunsaturated and contained high concentrations of the omega-3 polyunsaturate, docosahexaenoic acid (22:6 (n-3)). In contrast, phospholipids from bearded dragon tissues contained higher proportions of monounsaturates and lower proportions of polyunsaturates. Sodium pump molecular activity was only moderately elevated in tissues of the octopus compared to the bearded dragon, despite the much greater level of polyunsaturation in octopus membranes. When the current data were combined with data for the ectothermic cane toad, a significant (P = 0.003) correlation was observed between sodium pump molecular activity and the content of 22:6 (n-3) in the surrounding membrane. These results are discussed in relation to recent work which shows a similar relationship in endotherms.
authors.affiliation: Department of Biomedical Science, Metabolic Research Centre, University of Wollongong, Wollongong, NSW, 2522, Australia. nigelt@uow.edu.au
authors.forename: Nigel
authors.initials: N
authors.lastname: Turner
authors.forename: A J
authors.initials: AJ
authors.lastname: Hulbert
authors.forename: Paul L
authors.initials: PL
authors.lastname: Else
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D002462:Cell Membrane; D008116:Lizards / Q000502:physiology*; D008563:Membrane Lipids / Q000737:chemistry*; D049831:Octopodiformes / Q000502:physiology*; D010743:Phospholipids / Q000032:analysis / Q000737:chemistry*; D000254:Sodium-Potassium-Exchanging ATPase / Q000494:pharmacology / Q000502:physiology*
chemical_list: D008563:Membrane Lipids; D010743:Phospholipids; D000254:Sodium-Potassium-Exchanging ATPase
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 1998 Feb;119(2):325-34
references.pmid: 9629666
references.citation: Am J Physiol Regul Integr Comp Physiol. 2004 Sep;287(3):R633-41
references.pmid: 15308503
references.citation: J Agric Food Chem. 2002 Dec 4;50(25):7314-22
references.pmid: 12452651
references.citation: Biochim Biophys Acta. 1968 Jan 3;150(1):41-6
references.pmid: 4230616
references.citation: J Comp Physiol B. 1999 Jul;169(4-5):296-302
references.pmid: 10466220
references.citation: Lipids. 1997 May;32(5):497-506
references.pmid: 9168456
references.citation: Comp Biochem Physiol Comp Physiol. 1992 Feb;101(2):387-93
references.pmid: 1348468
references.citation: Biochem J. 1991 Apr 1;275 ( Pt 1):81-6
references.pmid: 1850242
references.citation: Am J Physiol. 1981 Jan;240(1):R3-9
references.pmid: 6257122
references.citation: J Neurochem. 1987 Nov;49(5):1333-40
references.pmid: 2822851
references.citation: Am J Physiol. 1987 Jul;253(1 Pt 2):R1-7
references.pmid: 3605374
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 2000 Jul;126(3):387-96
references.pmid: 10964033
references.citation: Naturwissenschaften. 2003 Nov;90(11):521-3
references.pmid: 14610651
references.citation: J Nutr. 1993 Mar;123(3):512-9
references.pmid: 8463854
references.citation: Am J Physiol. 1994 Sep;267(3 Pt 2):R754-61
references.pmid: 8092319
references.citation: Biochemistry. 1988 Aug 23;27(17):6449-52
references.pmid: 2851324
references.citation: Am J Physiol. 1989 Jan;256(1 Pt 2):R63-9
references.pmid: 2536249
references.citation: Biochim Biophys Acta. 1988 Oct 20;944(3):344-50
references.pmid: 2846060
references.citation: Am J Physiol. 1996 Nov;271(5 Pt 2):R1287-94
references.pmid: 8945966
references.citation: J Biol Chem. 1957 May;226(1):497-509
references.pmid: 13428781
references.citation: Biochemistry. 2003 Jul 22;42(28):8541-9
references.pmid: 12859201
references.citation: Biochemistry. 2001 Jul 31;40(30):8842-51
references.pmid: 11467945
references.citation: J Sci Food Agric. 1972 Dec;23(12):1471-5
references.pmid: 4349773
references.citation: J Biol Chem. 1975 Jun 10;250(11):4178-84
references.pmid: 123922
references.citation: J Theor Biol. 1999 Aug 7;199(3):257-74
references.pmid: 10433891
references.citation: Proc Natl Acad Sci U S A. 2000 Jun 6;97(12):6362-6
references.pmid: 10823917
references.citation: Neurochem Res. 2002 Dec;27(12):1641-7
references.pmid: 12515317