Oxidative damage and lipid peroxidation in the kidney of choline-defficient rats

OSSANI, GEORGINA; REPETTO, MARISA

FRONTIERS IN BIOSCIENCES

FBS, Bioscience, Albertson

Lugar: New York, USA; Año: 2007 vol. 12 p. 1174 - 1183

1093-4715

Phosphatidylcholine constitutes about 45% in plasma and inner mitochondrial membranes, 50% in Golgi membrane and 60% in rough endoplasmic reticulum, nuclear and outer mitochondrial membranes. Choline is a quaternary amine and is one of the precursors for the synthesis of acetylcholine; it is required for the synthesis of phospholipids that constitute cell membranes. Reactive oxygen changes in membrane properties are considered early events in response to oxidative damage. Lipid peroxidation process plays an important role in the development of the renal damage. Renal lipid peroxidation was found in the necrotic as well in the prenecrotic stages of  kidneys of choline-deficient weanling rats. In order to study the pathogenesis of the renal damage of choline-deficient rats we study markers of oxidative damage in cellular homogenates and subcellular membranes in kidneys of choline-deficient weanling rats as well as in choline-supplemented controls. Weanling Wistar male rats were divided in two groups, one fed a choline deficient diet ad libitum (n=16, 4 killed after 3 days of dieting and 12 after 6 days), and the other fed a choline supplemented diet ad libitum as control. Animals were sacrificed after 3 or 6 days of taking the experimental or control diet, because previous studies have shown that renal lesions due to choline deficiency appeared around the 5 day. Both kidneys were removed and weighted. Histological damage was evaluated and tissue homogenates were prepared in a medium consisting of phosphate buffer, 120 mM potassium chloride, pH 7.4 for oxidative damage markers: tert-butyl hydroperoxide-initiated chemiluminescence (CL) and malondialdehyde (TBARS) determinations. Subcellular fractions as membranes of mitochondria, lysosomes and endoplasmic reticulum were isolated from rat kidney homogenates by a classical procedure using centrifugal procedures and were used for tert-butyl hydroperoxide-initiated chemiluminescence assay. The acute renal damage was grossly characterized by an increase in size and weight and purplish red discoloration. Necrosis involved mainly convoluted tubules characterized by increased eosinophilia. Kidneys from experimental animals sacrificed after 6 days of diet showed no alterations or histopathological tubular necrosis up to grade 4. TBARS were statistically significant in rats killed the third day of having the diet, showing in choline deficient rats an increase of 63% in malondialdehyde levels, while differences in cellular CL were statistically significant in those choline-deficient animals sacrificed the sixth day of having the experimental diet, showing an increase of 83% in the level of the maximal emission. Differences in CL were statistically significant in those choline-deficient rats sacrificed the sixth day in mixture of membrane structures (plasma, smooth and rough endoplasmic reticulum and Golgi membranes) (140% higher in the level of maximal emission), mitochondrial (42% higher in the level of maximal emission) and lysosomal membranes (143% higher in the level of maximal emission). In conclusion, these results suggest that the choline deficiency produces oxidative damage in kidney membranes in cellular as well as in subcellular levels. The increase of oxygen reactive species, triggered by NADH overproduction, might be the cause of mitochondrial and cellular oxidative damage in choline-deficient rats.