Lectin Histochemistry of Taste Buds of the Rat Tongue Circumvallate Papilla under Normal Conditions and in Glutamate-Induced Obesity

Sodium glutamate in the form of a dietary supplement causes metabolic disorders and can induce obesity and digestive tract diseases. The purpose of the research was to study the influence of sodium glutamate on the carbohydrate determinants of taste buds of the rat tongue using a set of 6 lectins with different carbohydrate specificities. It is well known that violation of cellular homeostasis leads to changes in their glycocode, which, in turn, serves as one of early and objective signs of the onset of pathological process. Lectins allow not only the identification of carbohydrate determinants of cell and tissue glycoconjugates, but also to study their redistribution in the dynamics of their exposure on plasma membranes, intra- and extracellularly under physiological and pathological conditions. Material and methods. The experiment was conducted on 20 male rats weighing 180-200 g (10 control and 10 experimental). The experimental model of alimentary obesity was reproduced by adding an inducer of food consumption – sodium glutamic acid salt – in a ratio of 0.6: 100.0 to a high calories diet for 30 days. After determining body weight of experimental animal, it was calculated the weight of the feed mixture, which consisted of standard food (47%), sweet concentrated milk (44%), corn oil (8%), and vegetable starch (1%). Indicators obtained while measuring body's parameters of experimental animals confirmed the development of obesity in rats that were fed with sodium glutamate supplementation: the body mass index (BMI) in the control group animals was 0.66 ± 0.04, while BMI of the experimental group animals was 0.75 ± 0.03, p < 0.001. The body length of control and experimental group animals was not significantly different. Histological material (tongue) was fixed in Bouins fluid, dehydrated and embedded in paraffin. Results and discussion. Carbohydrate determinants were detected by lectin-peroxidase technique using a set of 6 lectins: LABA (αLFuc specific), RCA (βDGal), WGA (DGlcNAc > NeuNAc), CNFA (GalNAcβ1-˃4GlcNAc, (LacdiNAc)), CCRA (DGalNAc), GNA (αDMan specific) with subsequent visualization of lectin receptor sites in diaminobenzidin-H2O2 medium. Microscopic investigation was performed using «Granum R6053» microscope, equipped with «Echoo-Imager 502502000» camera and the computer program «ToupView 3.7». It was detected that glutamate-induced glycoconjugate rearrangement included substantial reduction of αLFuc, βDGal, DGlcNАc, NeuNAc and GalNAcβ1-˃4GlcNAc, (LacdiNAc) determinants in the cytoplasmic glycoconjugates of sensory and supportive cells of taste buds, which was accompanied by the accumulation of RCA, WGA and CNFA lectin receptor sites predominantly in the surface epithelial layer of lingual mucosa. Conclusions. Changes of glycoprofile under the influence of sodium glutamic acid salt apparently cause subsequent changes in the permeability of the plasma membranes of sensory cells of taste buds, which is likely to change their taste sensitivity. The reduction of LABA, RCA, WGA and CNFA lectins receptor sites within the taste pores of rats affected with glutamate-induced obesity may be associated with the decreased secretion of glycoproteins by supportive epithelial cells.