The association of gap junctions with large particles in the crypt epithelium of the rat small intestine.

Intercellular junctions in the epithelium of the rat small intestine were studied by the freeze-fracture method. Gap junctions were found between columnar cells of the crypt far more frequently than between absorptive cells of the villus. In addition, in the crypt, large particles 11 to 13 nm in diameter were often associated with the gap junction which primarily consisted of usual gap junctional particles 8 to 9 nm in diameter. Both the usual and large particles possessed a central pit. The intestinal crypt is the site of epithelial cell proliferation and differentiation in the process of physiological cell renewal. The predominant presence of gap junctions in this region suggests that they play a certain role in the proliferation and differentiation of crypt columnar cells. Further studies are required to elucidate the nature of the large particles, a precursor of typical connexons and/or a functionally different gap junction.