Changes in intestinal alkaline phosphatase in bowel ischemia

Abstract

With the use of the specific substrate inhibitor, L-phenylalanine, the intestinal component of serum alkaline phosphatase was determined in dogs subjected to various intestinal devascularization procedures. In the group of dogs with superior mesenteric artery occlusion, the intestinal contribution of serum alkaline phosphatase gradually fell from a control value of 25 to 0 per cent in four of five animals. Selective devascularization of the proximal half of the small intestine in three dogs produced a similar pattern but there was little or no change in another three dogs when the distal half of the bowel was rendered ischemic. These studies suggest that an adequate blood supply is required for the intestinal elaboration of alkaline phosphatase and that the enzyme production most likely occurs in the proximal small intestine. Histochemical confirmation of the aforementioned results was obtained in an additional four dogs. After anesthesia, control full-thickness biopsy specimens were taken from the jejunum and ileum. The superior mesenteric artery was ligated and biopsy specimens taken again one-half, one, and two hours after ligation. Sections 7 μ in thickness were stained with 5 iodo-indoxyl phosphate in Veronal-hydrochloric acid buffer of pH 9.O. This stain is specific for alkaline phosphatase. In the jejunal specimens the enzyme was concentrated in the tips of the villi and had almost completely disappeared two hours after mesenteric occlusion. There was only a small amount of enzyme in the ileum and there was little change produced there by mesenteric vascular occlusion. Theoretically, determination of the intestinal fraction of total serum alkaline phosphatase might be a useful tool in the clinical diagnosis of superior mesenteric artery obstruction.