Effect of Piper longum Linn.(pippali) in monosodium glutamate toxicity in rats

Abstract

The present study was conducted to evaluate the effect of ethanolic extract of fruits of Piper longum in monosodium glutamate toxicity in rats. Treatment as well as protective effects of the plant extract against MSG toxicity were studied.

The experiments were carried out in adult male Wistar rats, which were divided into seven groups. The treatment study was conducted in four groups viz; G0- normal control, G1-positive control, G2 and G3- two treatment groups. G1, G2 and G3 were administered with MSG at a dose rate of 8 mg/g body weight p.o. for 20 days followed by treatment of G2 and G3 with Piper longum extract at dose rates of 300 mg/kg and 600 mg/kg b.w p.o. respectively for 14 days.. Blood collection and weight recording of these animals were carried out on days 0, 21, 28 and 35 of experiment and then the animals were euthanized. The remaining three groups viz; G4, G5 and G6 were subjected to protective study where G4 served as normal control, G5, positive control and G6 was administered with Piper longum extract at 300 mg/kg dose rate along with MSG for 20 days. Blood samples were collected and the animals were weighed on days 0 and 21 of experiment followed by euthanasia.

The oxidative stress and subsequent damage to liver and kidney were assessed by measuring the biochemical parameters viz; activities of serum ALT, AST, concentration of serum triacylglycerol, total cholesterol, bilirubin, total protein, albumin, A:G ratio, urea, creatinine and the levels of serum and tissue (liver and kidney) lipid peroxides and GSH. From the euthanized animals liver and spleen were separated and weighed. Representative samples of liver and kidney tissues were subjected to histopathological examination.

Administration of MSG induced a significant increase in the body weight, weight of liver and spleen. The increase in body weight was gradual and became significant only on day 35. Oxidative injury to the tissues of liver and kidney was evident from the increased level of lipid peroxides, decreased level of GSH and increased activities of serum ALT and AST. There was also an increase in the levels of serum triacylglycerol, cholesterol and urea. Histopathological examination of the liver and kidney of positive control animals revealed necrosis of hepatocytes in the para cortical and midzonal areas of liver and diffuse cortical tubular degeneration, occasional necrosis and shrinkage of glomeruli of the kidney. However, the hepatic and nephro toxicities caused by MSG were not so severe to alter the levels of total protein, albumin, A:G ratio, bilirubin and creatinine in serum.

Piper longum extract at both the dose levels proved to be effective in treating the toxicity induced by MSG and helped to bring back the body weight and weight of spleen near to that of the control, significantly reduced the lipid peroxides and increased the GSH levels in serum, liver and kidney. Treated groups also showed a significant reduction in serum ALT and AST activity, ameliorated the MSG induced hyperlipidemia and normalized the histological architecture of both the liver and kidney. Among the two dose rates, only the 300 mg/kg dose rate was effective in maintaining the liver weight near to that of the control and this dose rate was found to be more effective in alleviating the toxicity caused by MSG.

Co-administration of Piper longum extract and MSG prevented the abnormal increase in the weight of vital organs, level of lipid peroxides in serum, liver and kidney, while no increase was observed in the level of GSH. Significant decrease was also observed in the levels of serum AST, triacylglycrol and total cholesterol, whereas no change was observed in the level of ALT and urea. Although, ethanolic extract of Piper longum fruits at 300 mg/kg dose rate could offer significant protection against the induction of toxicity by MSG, it appears that the dose rate is insufficient to provide a complete protection against the oxidative injury.