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.
Subject(s)
Kidney Cortex/ultrastructure , Membrane Lipids/chemistry , Microvilli/chemistry , Animals , Cholesterol/chemistry , Fatty Acids/chemistry , Fatty Acids, Unsaturated/chemistry , Intracellular Membranes/chemistry , Intracellular Membranes/metabolism , Kidney Cortex/metabolism , Male , Membrane Fluidity , Membrane Lipids/metabolism , Monosaccharide Transport Proteins/metabolism , Phospholipids/chemistry , Rats , Rats, Inbred SHR , Rats, Inbred WKYABSTRACT
BACKGROUND: Na+-dependent D-glucose and D-galactose transport was studied in the ileal brush-border membrane vesicles from both spontaneously hypertensive rats (SHR) and their normotensive genetic control Wistar-Kyoto (WKY) rats. Initial rates and accumulation ratios of the transport of both monosaccharides were significantly lower in the hypertensive rats compared to the WKY rats. METHODS: In order to determine whether such modifications are related to morphological abnormalities, ileal epithelium of SHR and WKY rats was examined by light and electron microscopy. In addition, immunohistochemical and immunocytochemical localization of Na+-glucose cotransporter (SGLT1) was performed. RESULTS: Light microscopy studies showed hypertrophy in the ileal villi of hypertensive rats, with an increase in the villus width when compared to those from normotensive rats. Immunohistochemical studies of SGLT1 showed the protein localized in the apical membrane of the absorptive epithelial cells, along the entire villus. No changes between SHR and WKY rats were noted in the intensity and distribution of the SGLT1 protein along the villus-crypt axis. Electron microscopy studies showed a patchy loss of microvilli in the ileal enterocytes of SHR, compared to those from WKY rats. Immunocytochemical studies of SGLT1 were carried out by the immunogold method. Colloidal gold particles were localized at the ileal microvilli of normotensive rats. No significant presence of SGLT1 was found in the smooth apical surface of ileum from hypertensive rats, although most adjacent microvilli were marked. CONCLUSION: Morphological changes were accompanied by modifications in the sugar transport and in the immunolocalization of SGLT1 in the ileal epithelium of SHR.
