CLASSIFICATIONS OF ANTERIOR PITUITARY CELL TYPES WITH IMMUNOENZYME HISTOCHEMISTRY

Peroxidase-labeled antibody method was used to localize the six hormones of the anterior pituitary gland of male rats both at the light and electron microscopic levels. Growth hormone (GH), adenocorticotropic hormone (ACTH), prolactin and thyrotropic hormone (TSH) were found in separate cells. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were frequently found in the same cell. TSH cells were scarce and were located at the periphery of the gland. The anterior-ventral portion of the gland contained few or no GH cells, ACTH cells, prolactin cells and TSH cells, but was filled with gonadotropic cells. In an area near the intermediate lobe, GH cells, ACTH cells and TSH cells were not found. GH cells and prolactin cells may be identified in electron micrographs without the aid of immunocytochemistry; however, ACTH cells and TSH cells may not be distinguished by their ultrastructural characteristics alone. Gonadotropic cells may be identified but their hormone content cannot be determined. The positive identification of these latter four cell types requires immunocytochemical methods.