Ultrastructure of endocrine cells in metaplastic epithelium of human gall bladder.

Two endocrine cell types were found in the metaplastic epithelium of gall bladders removed for gall stones. The endocrine cell type I resembled the EC (enterochromaffin) cell of the normal stomach mucosa. The homogeneous and electron-dense secretory granules were variable in size and shape and mainly located in the sub-nuclear cytoplasm. The endocrine cell type II was similar to the ECL (enterochromaffin-like) cell of the human stomach. The secretory granules were almost exclusively present in a subnuclear location, and were round and homogeneous in size. The secretory material was slightly granular and often there was a clear zone (halo) between the granule core and the limiting membrane. A rich network of microfilaments in the cytoplasm, especially around the nucleus, was typical of the type II endocrine cell. Both cell types were closely related to the basement membrane and the capillaries underneath.