Abnormalities in lipid composition of brush-border membranes isolated from renal cortex of spontaneously hypertensive rats

Abstract

The lipid composition and fluidity in brush-border membrane vesicles (BBMV) isolated from renal cortex of spontaneously hypertensive rats (SHR) and their normotensive control, Wistar Kyoto (WKY) rats have been studied. The activity of Na +-dependent D-glucose transport has been also determined. A significant increase in total phospholipids and free cholesterol were observed in renal BBMVs from SHR, which led to a decrease in the ratio of phospholipid-to-free cholesterol in these hypertensive rats. A reduction in the content of phosphatidylcholine and an increase in the percentage of sphingomyelin were observed in SHR. As a consequence, a diminished ratio of phosphatidylcholine-to-sphingomyelin was present in kidneys from SHR. The content of phosphatidylserine and phosphatidylinositol was reduced in SHR. However, the levels of phosphatidylethanolamine, cardiolipin, and lysophosphatidylethanolamine were increased in hypertensive animals. An increase in the level of saturated fatty acids, together with a decrease in the level of unsaturated fatty acids was responsible for the lower ratio of unsaturated-to-saturated fatty acids found in kidneys from SHR. The ratio of linoleic-to-arachidonic acid was increased in SHR when compared to WKY rats, as a result of the observed decrease in the content of arachidonic acid in hypertensive rats. Studies of diphenylhexatriene fluorescence polarization indicated no changes in the fluidity between BBMVs from both experimental rats, which did not correlate to the observed changes in the lipid composition of these membranes. These modifications in brush-border membrane lipid composition were accompanied by changes in the Na +-dependent d-glucose transport through renal BBMVs from SHR.