RENAL BRUSH-BORDER MEMBRANE LIPID-COMPOSITION IN BASENJI DOGS WITH SPONTANEOUS IDIOPATHIC FANCONI-SYNDROME

To comprehend the renal defect underlying idiopathic Fanconi syndrome in the Basenji dog, we have focused on delineating the lipid profiles of renal brush border membranes isolated from affected and normal Base nji dogs to establish any physical or compositional changes underlying previously observed transport and membrane-fluidity changes. The lipi d composition was studied with respect to total lipid, cholesterol, an d phospholipid content, cholesterol to phospholipid ratio, distributio n of the major phospholipid classes, and fatty acid composition. Total phospholipid of the isolated renal brush border membranes from Fancon i syndrome dogs analyzed by P-31 nuclear magnetic resonance showed no difference compared with that of normal dogs. Examination of total fat ty acids in both membranes using gas-liquid chromatography analysis of fatty acid methyl esters showed no difference in the mole percents of the major fatty acids. Our data suggest that changes in bulk membrane fluidity of the Fanconi syndrome dog renal brush border as measured b y 1,6-diphenyl-1.3.5-hexatriene cannot be attributed to phospholipid a nd fatty acid compositional change. In the membranes isolated from aff ected dog kidney, the cholesterol content determined by gas-liquid chr omatography analysis was 66 mol% higher than in membranes isolated fro m normal dog kidney. This correlates with the higher cholesterol to ph ospholipid molar ratio of 0.82 +/- 0.08 in the affected animal as comp ared with 0.58 +/- 0.04 in the normal. Cholesterol content and its mic rodomain in the membrane bilayer may be important in modulating transp ort functions. Increased membrane cholesterol content may affect the c onformational motility of membrane transport proteins and thus affect their function. Copyright (C) 1994 by W.B. Saunders Company