Intestinal mucosal permeability allows some molecules to pass
through the gut wall by simple diffusion. When stressors and other
adverse factors occur, the permeability of the gut may be altered before
histology and morphologic changes develop, allowing viable bacteria
and endotoxin from the gastrointestinal tract to pass through the
epithelial mucosa into the lamina propria and the mesenteric lymph
nodes, and possibly other organs (Berg and Garlington, 1979). Endotoxin
is a metabolite of Gram-negative bacteria and is part of the composition
of their cell wall; diamine oxidase is an endocellular enzyme of the
villous cells of mammalian mucous membranes; and D-lactate is a
metabolite of bacterial fermentation. Under normal circumstances, no
endotoxin, diamine oxidase, or D-lactate can pass through the epithelial
mucosa, and their presence in blood is an indicator of intestinal
permeability (Luk et al., 1983). In the current study, on day 21, the
blood concentrations of endotoxin and diamine oxidase in the
palygorskite groups were significantly lower than those in the control
group, which indicated that dietary supplementation with palygorskite
may protect the gut mucosa. However, no differences between the
control and palygorskite groups were observed on day 42, and this
may be because the gut barrier function of the experimental pigs on
day 42 was relatively mature and less vulnerable to damage.