Immunocytochemical localization of hepatic fatty acid binding protein in the rat intestine: effect of fasting.

Localization of hepatic fatty acid binding protein (h-FABP) in the small and large intestines of rats was studied by light and electron microscopic histochemistry using the peroxidase-antiperoxidase (PAP) method. In the small intestine of rats fed ad libitum, an intense FABP immunoreactivity was confined to the absorptive epithelial cells of the villi, but not of the crypts. The lowest margin of the immunoreactive cell sheet was closer to the crypts in the proximal than in the distal portions of the small intestine. In the large intestine, FABP immunoreactivity was present in the surface epithelial cells, with higher intensity in the proximal than in the distal portions of the intestine. After fasting rats for two days, many crypt cells exhibited intense immunoreactivity for h-FABP, resulting in an extension of the lowest margin of the immunoreactive cell sheet deep into the crypts. Such expansion of the immunoreactive cell population was reversed by refeeding the animals. With regard to the intracellular localization of immunoreactivity in the jejunum, the basolateral portion of the cytoplasm exhibited a more intense immunoreaction than the apical portion in the majority of immunoreactive cells lining the villi, whether the animals were fed or fasted. The immunoreactive products appeared in the cytoplasmic matrix without association with any subcellular structures.(ABSTRACT TRUNCATED AT 250 WORDS)