Functional classification of cell types in the growth hormone‐ and prolactin‐secreting rat MtTW₁₅ mammosomatotropic tumor with ultrastructural immunocytochemistry

Abstract

The aim of this study was to identify the neoplastic endocrine cells which contain growth hormone (GH) and prolactin (PRL), in the MtTW15 mammosomatotropic tumor, with ultrastructural immunocytochemistry. We used tumors recovered after 5 to 11 weeks of tumor development, from normal (untreated) rats and from rats treated with the progestin medroxyprogesterone acetate (MPA)--a stimulator of GH secretion in these tumors. Immunocytochemical staining was done with the peroxidase-antiperoxidase technique on ultrathin sections of tumor that had been fixed in glutaraldehyde and postfixed on osmium tetroxide. Immunospecific staining for PRL was found over small (150 nm) secretion granules, whereas staining for GH was deposited on the larger secretion granules (250 nm). Tumors from MPA-treated rats contained profuse numbers of neoplastic cells with large, GH-positive granules. Immunocytochemical staining for GH and PRL was also found in crinophagic, lysosome-like inclusions, particularly in cells that contained many secretion granules. The results support the hypothesis that GH and PRL are produced by separate neoplastic endocrine cell types in the MtTW15 mammosomatotropic tumor, and demonstrate the value of ultrastructural immunocytochemical analysis for functional classification of cell types in chromophobic pituitary adenomas.

Ultrastructure of spontaneous and transplanted pituitary tumors in laboratory animals

“…Baskin et al, 1980;Lloyd et al, 1985a;Makino et al, 1984;McComb et al, 1984;Parsons et al, 1980;Schelin et al, 1964;Trouillas et al, 1984. Classification of Transplantable Pituitary Tumlors Many transplantable pituitary tumors have been established and successfully maintained by serial transplantation. The tumors that have been studied most extensively include the MtTIW5, MtT/W10, MtT/W15, MtT/F4, and 7315a.…”

“…Other techniques that have been used to induce pituitary tumors include blocking hormone synthesis with drugs such as propylthiouracil which affects thyroid hormone synthesis and use of pituitary isografts in various sites such as the anterior chamber of the eye and kidney capsule which can lead to PRL cell hyperplasia and tumor development. Baskin et al, 1980;Lloyd et al, 1985a;Makino et al, 1984;McComb et al, 1984;Parsons et al, 1980;Schelin et al, 1964;Trouillas et al, 1984. Classification of Transplantable Pituitary Tumlors Many transplantable pituitary tumors have been established and successfully maintained by serial transplantation. The tumors that have been studied most extensively include the MtTIW5, MtT/W10, MtT/W15, MtT/F4, and 7315a.…”

“…However, the gland does not return to the pretreatment weight when compared with the control pituitary glands. Baskin et al (1980) examined the ultrastructural features of the MtT/W15 transplantable tumors with immunocytochemical labeling and found that PRL cells had small secretory granules with a mean diameter of 150 nm while GH was present in larger granules with a mean diameter of 250 nm. The studies of Parsons et al (1980) with immunocytochemistry revealed that many cells in the MtT/W15 tumors produced either PRL or GH, but that a small percentage of cells produced both PRL and GH.…”