ZnO and TiO₂ Nanocolloids: State of Mechanisms that Regulating the Motility of the Gastrointestinal Tract and the Hepatobiliary System

Abstract

Using the transmission electron microscopy (TEM)/high-resolution TEM (HRTEM) and selected area electron diffraction (SAED) methods, it was shown that the nanocolloids of ZnO contain hydrolyzed ZnO nanoparticles (NPs). Typically, the nanocrystalline ZnO/Zn­(OH)2 core is covered by an amorphous shell of zinc hydroxides, preventing the encapsulated crystal core from dissolving. Similar studies were carried out with TiO2 nanocolloids. It was found that burdening of rats for 30 days with a ZnO aqueous nanocolloid (AN) was accompanied by a narrowing of the amplitude range, a decrease (increase) in the frequency of spontaneous contractions (SCs), and an inhibition of the efficiency indices for smooth muscles (SMs) of the antrum and cecum. Under longer (100 days) burdening of rats with AN of ZnO, there was a tendency toward restoring the above parameters. In terms of the value and the direction of changes in most parameters for SCs of SMs, the effects (30 days) of TiO2 AN differed from those for ZnO AN and were almost the same in the case of their long-term impact. It was found that mostly M2-cholinoreceptor-dependent mechanisms of regulating the intracellular concentration of Ca2+ were sensitive to the effect of ZnO and TiO2 ANs. The molecular docking demonstrated that ZnO and TiO2 NPs did not compete with acetylcholine for the site of binding to M3 and M2 cholinoreceptors but may impact the affinity of orthosteric ligands to M2 cholinoreceptors. The studies showed that burdening rats with ZnO and TiO2 ANs was also accompanied by changes in the activity state of both intracellular enzymes and the ion transport systems for Na+, K+, and Ca2+, related to the processes of bile secretion, via the plasma membrane of hepatocytes.

Mechanisms of regulation of motility of the gastrointestinal tract and the hepatobiliary system under the chronic action of nanocolloids

“…3, 4.3, 5.3). A comparison of the above results with the previously obtained data 2 about the state of the mechanisms of regulation of the spontaneous contractile activity of SMs in different parts of GIT under short-term (30 days) intragastrically burdening of rats with TiO 2 AN showed (Figs. 3, 6) that they underwent the greatest changes under the long-term exposure, while under otherwise the same conditions, the results of burdening with ZnO AN were the opposite.…”

“…According to the literature 31 , age-related changes in the body cause partial loss of ICC (13% per decade for the human body aged 25-74 years) and the development of pathologies. A comparison of the above values of the spontaneous contractions parameters of the antrum piloricum and caecum SMs of rats (control group, age eight months) with the values of the corresponding parameters in rats of the younger age group (control group, age three months), reported in our previous study 2 , showed that in the older age group of rats, the frequency of spontaneous contractions of both the antrum pyloricum and the caecum SMs was almost twice lower than in the younger age group, n = 12. The duration of contraction-relaxation cycles increased; the amplitude ranges were nearly identical, whereas the amplitudes of contractions of the antrum SMs were three times higher than the corresponding value for the younger age group.…”

“…Biochemical markers. The rat blood plasma was obtained by centrifugation of whole blood and immediately used to determine biochemical markers of the functional state of the liver (the activity of alanine aminotransferase and aspartate aminotransferase, bilirubin concentration, and the thymol test) and lipid concentrations 2 . ALT and AST activities were determined by Reitman-Fresnel method, total and direct bilirubin were determined by Endraschik method and thymol test was performed using thymol reagent checking the test kits (R&D enterprise Felicity-Diagnostics, Ukraine).…”