Adverse effects in kidney function, antioxidant systems and histopathology in rats receiving monosodium glutamate diet

We investigated the effects of adding of monosodium glutamate (MSG) to a standard diet on oxidative stress in kidney, nitric oxide excretion, renal ions handling and blood pressure. We examined the association of these changes with the effects on renal histology. The study was performed on male Wistar rats (5 weeks old) divided into 3 groups: 1) MSG group were fed a diet supplemented with 3 g of MSG/kg b.w./day, five days a week, and spontaneous ingestion of a 1% MSG solution during 16 weeks; 2) NaCl group were fed a diet with NaCl (1 g/kg b.w./day) and 0.35% NaCl solution permanently alone at the same frequency and time; 3) control group were fed the normal chow and tap water. Sodium, potassium, calcium, phosphorus, creatinine, protein and nitric oxide excretion were analyzed in urine. We utilized clearance techniques to examine glomerular filtration rate and cortical renal plasma flow. We determined the oxidative state and the histopathological changes of renal tissue.

Following MSG treatment, absolute and fractional sodium and potassium excretion decreased although there was hyperfiltration. The MSG group showed similar increase in blood pressure than the NaCl group, but nitric oxide excretion was significantly reduced. Although no increase in lipid peroxidation was verified, its observed alteration in the reduced glutathione/oxidized cycle and their enzymes GPx and GR. These changes were accompanied by alterations histological both glomerular as well as tubular level and by interstitial fibrosis with mononuclear cells accumulation.

These results indicate that the addition of MSG in the diet decreases the excretion of Na, K and water with hyperfiltration. NaCl retention that leads to hypertension was accompanied by renal pathologic changes, intrarenal oxidative stress and reduction of nitric oxide excretion.