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 decreasein 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.