Experimental silicon intake with drinking water affects the serotonin supply in the digestive tract of laboratory rats

Abstract

Serotonin plays an important role in the function of the gastrointestinal tract. Currently, the dietary supplementation containing silicon becomes very popular trend, even for the long‐time reception. The effect of dietary silicon intake on serotonin level in small intestine (SI) and liver are not well understood. In this study we checked the impact of water‐soluble silicon compounds intake on the serotonin supply in structures of SI and liver.The study was curry out on 2‐months‐old male rats, which were divided on two groups: control group (n=10) received ad libitum drinking water; experimental group (n=10) received ad libitum the same water containing sodium metasilicate (Na2SiO3x9H2O, 10 mg/liter) for 2 and 9 months. Five animals from each group were sacrificed 2 months after beginning of the experiment, the rest – 9 months later. All manipulations with experimental animals were performed in accordance with the Regulations on Animal Experiments and in Compliance with European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes. The liver and pieces of small intestine (10 sm below the hepatoduodenal ligament) were isolated after decapitation and immediately frozen for the luminescence‐histochemical study. The presence of serotonin was detected on 10 µm cryosections using Falck‐Hillarp method modified by Krokhina (1982). The sections were examined under the Leica D1000 fluorescent microscope (360 nm of exciting light length, 525 nm of emission wavelength). Spectrofluorimetry was used to identify and quantify the serotonin levels in cytoplasm of follow structures: epithelial cells of mucous membrane, in the macrophages of the lamina propria of SI, in hepatocytes and luminescent granular cells (LGC) of liver.There are no significant differences in intensity of serotonin fluorescence in investigates structures of SI between control and experimental groups were detected after 2 months from the beginning of experiments. However, in liver the value of serotonin fluorescence intensity in the wall of the central veins and hepatocytes of rats in experimental group was elevated in 1.2 times, in LGC and their microenvironment – 1.5 times (р < 0,05) compared to the control group.The 9‐months silicon supplementation leads to the up‐regulation of serotonin fluorescence intensity in structures of SI: in cytoplasm of epithelial cells of the mucous membrane, in macrophages of the lamina propria and in their microenvironment, by 1.2 and 1.4 times, respectively (p < 0.05). The intensity of serotonin value in cytoplasm of hepatocytes and in the wall of the central veins of liver increased by 1.2 and 1.1 times, respectively (p < 0.05), in LGC and their microenvironment – by 1.3 and 1.7 times, respectively (p < 0.05).We concluded that (i) the liver is a little more sensitive to the intake of silicon with drinking water than the structures of SI; (ii) the silicon supplementation generally increases the intensity of serotonin content in structures of liver and SI, which can be explained by age‐related changes in these organs.