摘要：

The human colon carcinoma cell line Caco-2 grown in vitro under standard culture conditions in the absence of inducers of differentiation spontaneously exhibits signs of structural and functional differentiation and polarization. The differentiation is total at late confluency. Transmission and scanning electron microscopy show that the entire upper side of the monolayer is covered with typical brush border microvilli which extend perpendicularly to the surface. The asymmetry of the cells and the presence of tight junctions suggest that the monolayer is polarized. Functionally the differentiation is characterized by high levels of activity of the brush border associated enzymes. The levels of alkaline phosphatase and sucrase-isomaltase are nearly 50% of those found in similar preparations of human small intestine, and 10% in the case of aminopeptidase. The presence of the enzymes is further confirmed by the immunofluorescence staining of the cells with anti-sucrase-isomaltase antibodies. The functional enterocytic differentiation of the brush border microvilli is associated with the formation of domes which are typical of transporting epithelial monolayers. In the early proliferation phase of the culture 70% of the cells are structurally differentiated, but only a few of them are immunoreactive with anti-sucrase-isomaltase antibodies, and the enzyme activities are low.

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