Intestinal fatty acid binding protein in serum and urine reflects early ischemic injury to the small bowel.

BACKGROUND: Intestinal fatty acid binding protein (I-FABP) is a 15 kd protein that constitutes 2% to 3% of enterocyte protein. Normally I-FABP is undetectable in serum. The purpose of this study was to determine whether I-FABP could be detected in peripheral serum and/or urine early in the evolution of intestinal ischemic injury.
METHODS: I-FABP and two putative biochemical markers of mesenteric ischemia, hexosaminidase and lactate dehydrogenase, were quantitated in the serum of rats subjected to mesenteric ischemia produced by: (1) 0.5 hours, 1 hour, or 3 hours of superior mesenteric artery (SMA) occlusion followed by reperfusion; (2) 1 hour of mesenteric occlusion to a 10 cm segment of jejunum followed by reperfusion; and (3) arterial ligation to a 10 cm segment of jejunum without reperfusion. I-FABP was also quantitated in the urine and intestinal mucosa of these animals.
RESULTS: The baseline serum I-FABP level was < or = 4.0 ng/ml in all animals. In control animals, I-FABP remained unchanged throughout the experiment. In the ischemia/reperfusion groups, I-FABP immediately appeared in the serum on reperfusion. With segmental arterial ligation, I-FABP was detected in the serum within 15 minutes. Urinary content of I-FABP rose 60 minutes after its initial appearance in the serum, and its elimination paralleled serum I-FABP levels. Serum hexosaminidase and lactate dehydrogenase levels only rose after 3 hours of SMA occlusion with reperfusion. One hour of SMA occlusion and reperfusion resulted in only mild to moderate mucosal injury, whereas 3 hours of SMA ischemia with reperfusion produced areas of transmural necrosis.
CONCLUSIONS: I-FABP is released into the peripheral circulation after reversible intestinal ischemic injury and has potential as a biochemical marker to facilitate the early detection of mesenteric ischemia.