LIPID AND FATTY-ACID COMPOSITION OF DIFFERENT FRACTIONS FROM RAT URINARY TRANSITIONAL EPITHELIUM

The phospholipid composition of rat urinary transitional epithelium (T E) and the fatty acid composition of microsomal, mitochondrial, cytoso lic, and plasma membrane (PM) subcellular fractions were investigated. PM marker enzymes and electron microscopy analysis were used to chara cterize the PM fraction, which showed a distinctive lipid composition compared to the general profile of PM from different sources. The leve ls of cholesterol and sphingomyelin were not enriched in the PM fracti on; on the other hand, the increased amounts of glycosphingolipids and phosphatidylserine, and the decreased level of phosphatidylcholine fo llowed the general features of a PM profile. This differential PM lipi d composition may reflect the unique morphology of this mammal TE, con sisting of concave plaques with an asymmetrical membrane unit. The dis tribution of the double bond across the PM indicated a higher unsatura tion of the inner relative to the outer part of the PM hemi-leaflet. i n addition, the presence of 20:3n-9 nonessential fatty acid in a norma l TE may represent a characteristic fatty acid metabolism of this epit helium.