The fine structure of the S-100 protein positive cells in the rat pituitary gland: an immunoelectron microscopic study.

We examined the fine structure of rat folliculo-stellate (FS) cells of the anterior pituitary and pituicytes of the neural lobe using immunoelectron microscopy for S-100 protein. The study proves that S-100 protein is solely expressed in the FS cells and pituicytes. However, the ultrastructural differences between these two cell types demonstrated in this study may argue against the hypothesis that the FS cells and the pituicytes have a common origin.