Chronic toxicity of monosodium glutamate on the reproductive system and some internal organs of zebrafish (Danio rerio)

Abstract

Monosodium glutamate (MSG) is commonly used to enhance the tastes food. It is composed of sodium salt and amino acids. Although MSG is considered safe at the consumption level, its adverse effects have been reported. The objective of this study is to evaluate the effects of MSG on the brain, liver, kidney, testes, and ovaries of zebrafish (Danio rerio) which were chronically exposed to MSG from the embryo stage to the adult stage. Additionally, the fertilization rate and hatching rate of zebrafish embryos were also analyzed. Zebrafish were randomly divided into four groups and treated with MSG at 0, 10, 100 and 1,000 mg/l, respectively for 60 days. Before sacrifice for histopathological study, the fishes in each group were mated and the embryos were collected and analyzed for the numbers, survival rate and hatching rate. The results showed that the liver and kidneys of fishes in the MSG-exposed groups had a significantly higher lesion score (P<0.05) compared to the control group. All fish from the MSG-exposed groups had diffuse hepatocyte swelling and hepatic congestion. Renal congestion and a decrease in the number of distal convoluted tubules were observed. Zebrafish from the 1,000 mg/l MSG-exposed group did not spawn after placing them in the mating tank. The number of embryos from the 100 mg/l MSG-exposed group was lower than the 10 mg/l MSG-exposed group and the control group. The survival rate of fertilized embryos (after 120 hours) from the 100 mg/l MSG-treated group was significantly lower than the control group. In summary, the results from this study showed that exposure to MSG for 60 days induced lesions to the liver and the kidneys and decreased the reproductive performance of zebrafish.