Gross morpho-biometry, histometry and immunohistochemical investigations of pituitary gland in the juvenile and adult male African giant rats (Cricetomys gambianus)

This work was designed to investigate the morphometry and immunohistochemical features of pituitary glands in the African Giant Rats (AGR). Adult and juvenile AGR were sacrificed and their brains harvested, and the pituitary glands were carefully dissected. The weight, length and width of brains and pituitary glands were subsequently measured. Sections were prepared and stained using Haematoxylin and Eosin (H&E), Cresyl-violet and periodic-acid-Schiff (PAS) for histological analysis. Immunohistochemical analysis was carried out with Glial-Fibrillary-Acidic-Protein (GFAP) and Ionized-Calcium-Binding-Adapter-Molecule 1 (Iba1). Grossly, the AGR pituitary gland is a somehow laterally extended, saddle-shaped organ that is dorso-ventrally flattened. The gray-coloured adenohypophysis (anterior-pituitary lobe) was bigger in size than the whitish neurohypophysis (posterior-pituitary lobe) on physical examination. Histometrically, the adenohypophyseal length was noticeably greater than that of neurohypophysis in both juvenile and adult. Similarly, the adenohypophyseal and neurohypophyseal width in adult were found to be more than that of juvenile. Also, the histological staining of the neurohypophysis and adenohypophysis were distinct. In the neurohypophysis, fibrous and protoplasmic pituicytes were observed among fibres and Herring-bodies. Chromophils and chromophobes were identified in the adenohypophysis and melanotrophs in the intermediate lobe. Immunohistochemistry showed pituicytes in the neurohypophysis, which was positive with GFAP-antibody. With Iba1-antibody, the neurohypophysis expressed a stronger positive immunolabelling to microglia as compared to macrophages in the adenohypophysis. In conclusion, the gross and microscopic characteristics of pituitary glands of the AGR are found to be similar to other rodents and mammals. We recommend further study to compare morphometrical parameters between male and females of this model.