Objective  To investigate the effect of walnut oligopeptides (WOPs) on digestive function-related gastric secretion and blood/serum indicators in rats and on small intestinal propulsion in mice.

  Methods  Totally 130 male Sprague-Dawley (SD) rats and 70 male ICR mice were included in the study. The SD rats were first randomly divided into two subgroups (70 in subgroup Ⅰ and 60 in subgroup Ⅱ). The 70 SD rats of subgroup I and the 70 ICR mice were then randomly assigned into three control groups (normal, model, and whey protein control), three WOPs treatment groups (at dosages of 220, 440 and 880 mg/kg·bw), and a WOPs plus bovine collagen oligopeptides (BCOPs), with 10 rats or mice in each group respectively. The group-specific treatment was conclucted by intragastric administration of once a day for 30 days for the rats and 7 days for the mice; the grouping and treatments in 60 SD rats of subgroup II were the same as those of subgroup I, except for the absence of model control group. By the end of the treatments, the rats of subgroup I underwent pyloric ligation and collection of gastric fluid for detecting gastric acid and gastric tissue pepsin and serum gastrointestinal-associated regulatory hormones were also measured; while, the rats of subgroup II had choledochal cannula for bile collection. After 7-day′s treatment, the mice had another gavage of loperamide hydrochloride for examination of small intestinal propulsive function.

  Results  Compared with those in the model control group, the free acid, total acid and total acid excretion of gastric juice were significantly higher and the pepsin activity was significantly lower in the WOPs dose groups (all P < 0.05). The content of growth inhibitory hormone in high WOPs dose (880 mg/kg·bw) group was significantly lower than that in the model control group; the rats with medium (440 mg/kg·bw) and high (880 mg/kg·bw) WOPs treatment and combined treatment of WOPs and BCOPs had significantly higher motilin, substance P, and gastrin than those in the rats of model control group. The small intestinal propulsion rates of the mice in WOPs dose groups were significantly higher than that of model control mice (P < 0.05 for all).

  Conclusion  WOPs can exert pro-digestive effect by regulating the secretions of gastric acid, pepsin, gastrointestinal hormone in rats and by promoting gastrointestinal peristalsis in mice.