Effects of fatty acid deficiency on the lipid composition and physical properties of guinea pig rough endoplasmic reticulum

Abstract

Twenty-six days of fat deficiency brought about a decrease of linoleic and an increase of oleic acid in rough endoplasmic reticulum (RER) of guinea pig liver. Arachidonic acid was only slightly decreased in some phospholipids whereas eicose-5,8,11-trienoic acid was not enhanced except in phosphatidyl-inositol. All these changes were relevant specifically in phosphatidylinositol molecules and less important in phosphatidylcholine and phosphatidylethanolamine. Fat deficiency did not modify the relative proportion of phospholipids and cholesterol. Therefore, fat deficient guinea pig microsomes are a good model to study the effect of unsaturated fatty acids on membrane properties. Fluorescent anisotropy of RER membranes, lipids and phospholipids labeled with diphenylhexatriene, was increased by the fat deficiency. The most important increase was observed in liposomes of a mixture of RER phosphatidylinositol, phosphatidylserine and sphingomyelin. A small change was found in phosphatidylcholine and phosphatidylethanolamine dispersions at 37 degrees C. The modification of the lipid unsaturation evoked fluorescent anisotropy changes. Temperature-dependent fluorescent polarization curves of RER membranes labeled with trans-parinaric acid did not show inflections in the temperature range from 5 to 45 degrees C but, RER lipids and phospholipids presented a phase separation at about 20 degrees C. This inflection point was not modified by the fat deficient diet. In those liposomes prepared with a mixture of RER phosphatidylinositol, phosphatidylserine and sphingomyelin, the inflection point was produced at about 37 degrees C.

Molecular species of phosphoglycerides in liver microsomes of rats fed a fat‐free diet

“…Appreciable amounts of the nonessential fatty acid 20:3n-9, which is present only in trace amounts in EFA-sufficient animals, appear as a consequence of EFA or fat-free diets in rat (10,12,13) but not in guinea pig liver microsomes (14)(15)(16)(17).…”

“…Several studies using spectroscopic methods such as fluorescence (14,16,17) or electron spin resonance (3,6,15) have indicated that EFA or fat-free diets affect the physical properties of different membranes, such as guinea pig liver microsomes (14)(15)(16)(17) or piglet jejunum brush border membranes (3,6). This is attributed to changes in the fatty acid composition of membrane lipids, since no changes are observed either in the phospholipid class distribution or in the relative content of cholesterol, phospholipid, and protein.…”

“…EFA-deficient and fat-free diets modify the fatty acid composition of several membranes in different species (3,(10)(11)(12)(13)(14)(15)(16)(17).…”