[Zinc acts as a protective agent on the mucosal barrier in experimental TNBS colitis]

The aim of this study was to analyze the effect of enterally given zinc on the impaired epithelial barrier function in experimental TNBS colitis in rats. Rats in therapy group were zinc-fed in therapeutic dose. 48 hours after induction of TNBS colitis the rats were killed, the distal colon was resected and mounted into an Ussing chamber. The following electrophysiological measurements were carried out: 1. Flux measurements for Na+ and mannitol as a parameter of paracellular permeability, 2. Resistance measurements of the colon, distinguishing between pure epithelial resistance and resistance of the subepithelial tissue. In TNBS colitis we found a marked increase of both fluxes as a parameter of enhanced paracellular permeability (factor 3). Further there was a drastic reduction of total resistance, and especially of pure epithelial resistance indicating a massive epithelial barrier defect. In rats treated by zinc the increase of paracellular permeability was increased only by a factor of 2, and there was only a moderate decrease of resistance. For the first time we demonstrated zinc to have a protective effect on damaged mucosal barrier function in TNBS colitis. These results confirm the data collected in guinea pigs with malnutrition, whose intestinal integrity could be improved by zinc. Further studies are necessary in order to test whether this protective effect of zinc on mucosa barrier in experimental colitis may be relevant also in human ulcerative colitis.