Influence of Bentonite Nanoclay on the State of the Rat Intestine Protective Barrier in the Experiment

Abstract

Bentonite nanoclays are widely used in the food industry as technological aids, that is, adsorbents in the purification of vegetable oils and in the production of beverages. Permitted food additives include sodium, potassium and calcium aluminosilicates (E554–E556), bentonite (E558), and kaolin (E559). The data on the oral toxicity of nanoclays (NCs) are few and contradictory. It is known that in vitro native and organomodified NCs exhibit cytotoxicity against both normal and transformed animal and human cells. Due to high ion-exchange and adsorption capacity, NCs can interfere with the absorption of trace elements in the gastrointestinal tract, in particular zinc. Nanoclays can affect the composition and activity of intestinal microbiocenosis. In an experiment on the subacute 92-day oral toxicity of bentonite NCs for Wistar rats it was shown that NCs at a dose of 100 mg/kg bw (body weight) prevent the permeation of chicken ovalbumin macromolecules through the intestinal barrier, which were not detected in the blood of all tested rats 3 h after its intragastric administration at a dose of 2000 mg/kg bw. In the same animals, a significant increase in absolute body weight was noted. The results of microscopic examination of the mucous membrane of the small intestine showed an increase in the secretion of the intestinal mucus with the formation of a dense mucous barrier at an NC dose of 10 mg/kg bw or more. The formation of this barrier already occurred with the localization over the brush border of enterocytes with an increase in the number of goblet cells at a dose of 10 mg/kg bw. At a dose of 100 mg/kg bw, together with a sharp increase in the number of these cells, a merged layer of the dense mucus was formed, sticking together the villi in the apical part. At the lowest of the studied NC doses (1 mg/kg bw), an increase in the desquamation of enterocytes in the apical part of the villi was observed. Morphometric analysis of the villus length and crypt depth showed that the villus/crypt ratio decreased under NC consumption within 32–34% compared with the control regardless of the dose of the nanomaterial. NC consumption in the entire range of the studied doses had a negative effect on the morphofunctional state of the villi and crypts of the rat ileum, while excessive mucus secretion at an NC dose of 100 mg/kg bw can disrupt parietal digestion and affect the barrier and immunoregulatory functions of the intestine.