Immunohistochemical and ultrastructural assessment of folliculostellate cells in rabbit pituitary gland at different ages

This study was performed on nine male Balady rabbits classified into three groups [three animals each]; young [3-months old], adult [6-8 months old] and old [20-months old]. At the time of scarification, the pituitary glands were dissected and processed for light and electron microscopy examinations. The immunohistochemical reaction to S-100 protein revealed a significant decline in the localization of the folliculostellate [FS] cells positively immunolabelled in the pars distalis of the old rabbit pituitary compared with the young and adult animals. By electron microscope, FS cells were found with clear cytoplasm, devoid of secretory granules and had long narrow processes, that intermingled with neighboring cells. They appeared in a close contact with all types of secretory cells, especially gonadotrophs. Cellular junctions sealed were detected either between the FS and hormone- secreting cells or linking two FS cells. Adult rabbit anterior pituitary showed FS cells with prominent RER. Many FS cells from the old rabbit pituitary showed dispersed heterochromatic nuclei and distorted mitochondria, vacuolated cytoplasm were often seen with numerous microvilli on their borders. Remarkable changes appeared with age in the different types of endocrine cells including vacuolated cytoplasm and dilated granular endoplasmic reticulum