| Neutral lipids of the plasma membrane: composition of plasma membrane fractions isolated from ocular lens. | |
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MedLine Citation:
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PMID: 9088744 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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PURPOSE: To quantitatively examine and compare the neutral lipid composition of sedimenting and non-sedimenting ocular lens plasma membrane fractions isolated from the cortex and nucleus. METHODS: Homogenates of bovine lens cortical and nuclear regions were subjected to centrifugation to sediment the water insoluble fractions, which were used as the sedimenting membrane fractions. The non-sedimenting membrane fractions were isolated from the water soluble fractions by flotation during overnight, high density centrifugation. Lipids were extracted from the membrane fractions and neutral lipids were separated by thin layer chromatography. RESULTS: A greater concentration of triacylglycerol was found in the whole lens non-sedimenting membrane fraction (10.6 micrograms triacylglycerol/mg phospholipid) than in the sedimenting membrane (3.7 micrograms triacylglycerol/mg phospholipid). Triacylglycerol was found in the non-sedimenting membrane fraction isolated from both lens cortex and nucleus, but was not detected in the water insoluble fraction isolated from the lens nucleus. The higher triacylglycerol concentration of the non-sedimenting membrane correlates with its lower cholesterol level. Free fatty acids were found in both the whole lens non-sedimenting membrane fraction (66.2 micrograms free fatty acid/mg phospholipid) and water insoluble fraction (40.3 micrograms free fatty acid/mg phospholipid). Free fatty acids were more abundant in the nucleus. This could reflect phospholipase attack of nuclear phospholipids, a mechanism proposed to explain the lower glycerophospholipid concentration in this region. The fatty acid compositions of the phospholipids from the non-sedimenting and sedimenting membrane fractions were essentially identical. Triacylglycerols (from both non-sedimenting and sedimenting membrane fractions) contained a greater proportion of saturated fatty acids and a lesser proportion of mono-unsaturated fatty acids than the phospholipids. The triacylglycerols of the non-sedimenting membrane fraction contained a greater amount of palmitic and lesser amounts of myristic and stearic acids than the triacylglycerols of the sedimenting membrane fractions. The free fatty acids (of both non-sedimenting and sedimenting membrane fractions) were composed of a greater proportion of saturated fatty acids and a lesser proportion of mono-unsaturated fatty acids than found in the phospholipids. The non-sedimenting membrane fraction of both cortex and nucleus was enriched with an unidentified (presumed) lipid. These findings support earlier work indicating most membrane triacylglycerols are enriched in saturated fatty acids. CONCLUSIONS: These results demonstrate differences in the neutral lipid composition between non-sedimenting and sedimenting lens membrane fractions and furthers our hypothesis that the non-sedimenting membrane could represent a specialized domain of the lens plasma membrane. |
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Authors:
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C R Fleschner; R J Cenedella |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: Current eye research Volume: 16 ISSN: 0271-3683 ISO Abbreviation: Curr. Eye Res. Publication Date: 1997 Mar |
Date Detail:
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Created Date: 1997-06-05 Completed Date: 1997-06-05 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 8104312 Medline TA: Curr Eye Res Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 263-9 Citation Subset: IM |
Affiliation:
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Department of Biochemistry, Kirksville College of Osteopathic Medicine, MO 63501, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Cattle Chromatography, Thin Layer Fatty Acids / analysis Lens, Crystalline / chemistry* Membrane Lipids / analysis* Phospholipids / analysis Triglycerides / analysis |
| Grant Support | |
ID/Acronym/Agency:
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EYO2568/EY/NEI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Fatty Acids; 0/Membrane Lipids; 0/Phospholipids; 0/Triglycerides |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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