Effects of soybean antigen proteins on intestinal permeability, 5-hydroxytryptamine levels and secretory IgA distribution in the intestine of weaned piglets

Abstract

In this experiment, the effects of soybean antigen proteins on intestinal permeability, 5-hydroxytryptamine (5-HT) levels and secretory IgA (sIgA) distribution in the intestine of weaned piglets were evaluated. Thirty piglets (21 d of age) were randomly divided into three groups: control group, glycinin-sensitised group and β-conglycinin-sensitised group. Piglets in the control group were fed a basal diet, and in two sensitised groups were fed the diet with 4% glycinin or β-conglycinin. Piglets in glycinin and β-conglycinin groups were sensitised twice on 21–27 d and 32–34 d period, respectively. Blood samples were collected and analysed for D-lactic acid, diamine oxidase (DAO) and 5-HT levels on d 21, 28 and 35. At the end of the trial, five piglets per group were sacrificed and the small intestine was collected to evaluate intestinal sIgA distribution and the optical density (OD) of the relative staining positivity. The results revealed that the piglets in glycinin and β-conglycinin groups had higher D-lactic acid, DAO and 5-HT levels than those of the control group (p < 0.01). Similarly, OD values were higher in the treatment groups than in the control group (p < 0.01). The intestinal sections, in order of decreasing OD value, were middle jejunum > duodenum > proximal jejunum and distal ileum > distal jejunum. These results suggest that soybean antigen proteins induce allergic reactions, damage the intestinal mucosa, increase intestinal permeability and promote sIgA synthesis in weaned piglets.