The effect of fatty acid perfusion on intestinal alkaline phosphatase

Abstract

The purpose of this and the following article is to document experimental evidence of the effect of fatty acid absorption and transport in the small-bowel mucosa on the activity of the intestinal isoenzyme of alkaline phosphatase. The first paper deals with perfusions of fatty acids of increasing carbon length into the duodenum of volunteers, studying changes in luminal concentrations and mucosal location of intestinal alkaline phosphatase. In the second paper, which follows, the preliminary observations in human studies have been investigated in more detail in a rat model. In 15 normal volunteers a segment of proximal small bowel was isolated by a four-lumen, two-balloon tube technique and perfused with micellar solutions of fatty acids (C8∶0, C12∶0, C18∶1) in a taurocholate solution. In control experiments the perfusion fluid lacked fatty acids. The luminal contents were enriched with intestinal alkaline phosphatase over control values as a function of the carbon-chain length of the fatty acids. The extent of sucrase release was less pronounced and that of glycylglycine dipeptidase was negligible. The effect of intraluminal oleic acid on the location of mucosal alkaline phosphatase activity was studied by histochemical techniques in small-bowel biopsies obtained in six additional subjects. Intestinal alkaline phosphatase activity appeared to be in the same location as the dynamic lipid transport, moving from the brush border into the mucosal lymphatics. Our studies indicate bidirectional flow of brush-border intestinal alkaline phosphatase into the bowel lumen and into the intestinal lymphatics during fatty acid absorption.