Immunomicroscopic localization of the 10,000 molecular weight calcium-binding protein in the human enterocyte

The cellular localization of the 10,000 molecular weight calcium-binding protein (CaBP or Calbindin-D) in the small intestinal epithelium of man was investigated by immunofluorescence and immunoelectron microscopy (immunogold staining). Indirect immunofluorescence on frozen sections showed intracellular staining in the enterocyte. The fluorescence was evenly distributed and no significant differences were observed between crypt and villus cells. No staining was found in goblet cells or in the submucosa. Correspondingly, immunogold labeled antibodies were scattered over the cytoplasm of the enterocyte. The terminal region appeared to be the most intensely decorated and the brush border region showed labeling above the background level. No labeling was associated with intracellular membranes or the basolateral membrane.