Histological and morphometric changes in thymus and blood lipid profile in white rats under the influence of sodium glutamate administration

Abstract

Introduction. The effects of monosodium glutamate (MSG) on animals and humans are mainly manifested in the form of metabolic disorders. The purpose of the study: to investigate the effect of 28-day oral administration of MSG at the rate of 30 mg/kg body weight on histological and morphometric parameters of the thymus, as well as blood lipid profile in rats. Object and research methods. The experiment was performed on 20 white nonlinear rats of reproductive age. The experimental animals were divided into two groups (10 rats in each group), which received daily oral administration of MSG at a dose of 30 mg/kg body weight. The effect of 14- and 28-day administration of MSG was studied in groups I and II, respectively (depending on the week of decapitation). Control rats (n=10) were administered placebo (0.5 ml of drinking tap water at room temperature) for 14 and 28 days. The intact control animals were also divided into two groups of 5 rats each, depending on the time of decapitation. The animals were weighed before decapitation. Serum lipid metabolism was determined, and histological and morphometric changes in the thymus were studied. Research results and their discussion. In 14 days after administration of MSG to rats at a dose of 30 mg/kg body weight, the thickness of the thymus capsule increases with maximum changes on day 28 of the experiment. In the thymus, initially, the administration of MSG leads to an increase in the relative area of the cortical substance and a decrease in the relative area of the cerebral substance; after 14 days (in rats of group 2), on the contrary, the area of the cortical substance decreases, accompanied by an increase in the relative area of the cerebral substance. The number of thymocytes in the cortical substance of the thyroid lobules increases after 14 days of exposure to MSG, and then the number of these cells gradually decreases. The number of thymocytes per 100 μm2 of cerebral substance also changes, i.e., with maximum values in rats of group 1 with a tendency to decrease by day 28 of the experiment. The administration of MSG to experimental animals of group 2 in the appropriate dosage up to 28 days contributed to a pronounced progression of lipid metabolism disorders in the blood serum of rats. This was manifested by an increase in total cholesterol (TC) in the blood serum by 1.8 times (p<0.001), triglycerides (TG) – by 3.5 times (p<0.001), low-density lipoprotein (LDL) – by 2.2 times (p<0.001), very low density lipoprotein (VLDL) – by 3.6 times (p<0.01) and a decrease in high density lipoprotein (HDL) – by 2.0 times (p<0.01). Conclusions. 1. The administration of MSG to rats at a dose of 30 mg/kg body weight leads to morphological changes in the structure of the thymus, namely, to an increase in the thickness of the organ capsule; an increase in the relative area of the cortical substance of the thymus after 14 days of MSG administration with its gradual decrease until day 28 of the experiment; the relative area of the cerebral substance, on the contrary, decreases after 14 days of MSG supplementation, and then gradually increases over the next 2 weeks of the experiment. 2. The administration of MSG to rats at a dose of 30 mg/kg body weight leads to lipid metabolism disorders, namely an increase in the level of TC, TG, LDL, VLDL and a decrease in HDL, with the most pronounced changes from the data of control animals on day 28 of the experiment.