Immunocytochemical localization of vimentin in stellate cells (folliculo-stellate cells) of the rat, cat and rabbit pituitary pars distalis.

The occurrence of vimentin, a specific intermediate filament protein, has been studied by an indirect immunoperoxidase method in the anterior pituitary gland of adult rats, cats and rabbits of both sexes. In the three species studied, the immunoreaction product was detected in the cytoplasm of stellate-shaped cells scattered throughout the pars distalis. These stellate cells showed long cytoplasmic processes which could be seen between the secretory cells, and occasionally, encircling them. These processes sometimes reach the vasculo-connective septa. The marginal cells lining the anterior layer of the hypophyseal cleft of the rat and the cat pituitary glands also showed a positive immunoreaction. Finally, cyst or follicle-like structures lined by immunostained cells with basal processes could be observed in the anterior lobe of the rat, but not in that of the rabbit or the cat. These findings support the previously held view that folliculo-stellate cells and marginal cells of the anterior pituitary gland have a common nature and suggest that these cell types might be derived from glial neuroectodermic cells.