ZnO and TiO(2) Nanocolloids: State of Mechanisms that Regulating the Motility of the Gastrointestinal Tract and the Hepatobiliary System

[Image: see text] 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 TiO(2) 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 TiO(2) 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 Ca(2+) were sensitive to the effect of ZnO and TiO(2) ANs. The molecular docking demonstrated that ZnO and TiO(2) 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 TiO(2) ANs was also accompanied by changes in the activity state of both intracellular enzymes and the ion transport systems for Na(+), K(+), and Ca(2+), related to the processes of bile secretion, via the plasma membrane of hepatocytes.