In the intestine, the cystic fibrosis transmembrane conductance regulator (CFTR) has been localized to the apical pole of crypt epithelial cells. Recent data indicate that some villus cells may also express CFTR, although the identity of these cells has not been established. The aim of the current study was to characterize the distribution, morphology, and surface marker expression of CFTR-expressing villus cells.

Immunofluorescence and immunoelectron microscopy was performed using anti-CFTR and enzyme marker antibodies.

In the rat and human proximal small intestine, a subpopulation of scattered villus and superficial crypt epithelial cells label brightly with anti-CFTR antibodies. The fluorescent signal is detected throughout the cells with its greatest concentration apically. At the ultrastructural level, labeling involves the brush border and a prominent subapical vesicular compartment. The cells resemble adjacent villus enterocytes in their abundance of mitochondria and expression of basolateral Na⁺-K⁺-adenosine triphosphatase yet differ in their absence of brush-border sucrase and lactase expression.

A previously uncharacterized subpopulation of villus cells with high levels of intracellular CFTR expression exists in the proximal small intestine. Morphological and cytochemical studies suggest that this subset of villus cells has a unique transport function.