Cholestyramine and bile diversion lower the aminopeptidase activity in the intestinal brush border membrane of rats
1993
Sonoyama, K. (Hokkaido Univ., Sapporo (Japan). Faculty of Agriculture) | Kiriyama, S. | Niki, R.
To examine the effect of bile acids on the activity of intestinal aminopeptidase in vivo, we measured the activity of aminopeptidase in the intestinal mucosa from rats fed the diet containing cholestyramine which sequesters luminal bile acids (experiment 1) and from bile diverted rats (experiment 2). After 32 h fasting, rats were refed for 16 h either of a standard diet (25% casein diets), the same diet containing cholestyramine, or the fat-free diet in experiment 1. In the intestinal washing, the content of total bile acids was markedly decreased with feeding cholestyramine and activities of trypsin and chymotrypsin were also lowered with cholestyramine. Cholestyramine feeding decreased the specific activity of aminopeptidase in the homogenate of intestinal mucosa but increased the specific activities of sucrase and alkaline phosphatase. All these parameters were not modified by the fat-free diet. In experiment 2, bile diverted and sham operated rats were refed the standard diet for 16 h with prior 32 h fasting. Bile diversion, like cholestyramine feeding, lowered the content of total bile acids, the activities of pancreatic hydrolases in the intestinal washings, and the specific activity of aminopeptidase in the intestinal mucosa. The specific activity of sucrase in the intestinal mucosa was higher in bile diverted rats but the activity of alkaline phosphatase was not changed. These data indicate that the decreased abundance of intraluminal bile acid affects the activity of intestinal aminopeptidase not through the decreased absorption of dietary lipid. We propose that the intraluminal bile acids may be important for maintaining the activity of aminopeptidase while the degradation of sucrase by the pancreatic proteinases may be accelerated by the bile acids
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