ABSTRACT
African giant rat is currently explored as a laboratory model for scientific research. In this present study, anatomical studies on the thyroid, parathyroid and adrenal glands of the African giant rat (Cricetomys gambianus,water house 1840) was evaluated with twenty adult African giant rats of both sexes. The architecture of the glands (thyroid, parathyroid and adrenal glands) was studied by gross observations and light microscopy. The mean weight of the African giant rat (AGR) was 1058.45 + 45.46g. Gross studies of the thyroid gland of the AGR showed a bi-lobed organ located on the lateral surface of the trachea. The two lobes of the gland were joined together towards the superior poles by an isthmus. Result showed that the weight of the male thyroid glands was significantly higher than that of the female African giant rat (P<0.05). The length and the width of gland do not show sexual dimorphism. Tetraiodothyronine showed sexual dimorphism. Histological studies showed that the thyroid of the African giant rat consisted of follicles surrounded by follicular cells of various shapes suggesting different level of activity of the follicles. Colloids in the follicles were stained positive with periodic acid Schiff stain indicating that glycoprotein was present. Parafollicular cells were present in between the follicles of the glands. Gross anatomy and morphological studies of the parathyroid glands of the African giant rat revealed that parathyroid glands were two pairs situated in the lateral and a little inferior in position to the thyroid gland. Histological studies showed that, the parathyroid glands were richly supplied with blood and the chief cells were abundant and arranged in form of cords throughout the glands. The chief cells were positive when stained with periodic acid Schiff stain which showed that glycoprotein was present. Hormonal assay of parathyroid hormone does not show sexual dimorphism. Gross anatomy and morphological studies of adrenal glands of the African giant rat showed that the paired adrenal glands were located on the superior poles of viii both kidneys: left and right kidneys. Result showed that the weight of the female adrenal gland were significantly higher than that of the male adrenal glands. There were no significant differences between the length and width of the male and female glands. Histological studies showed that the adrenal glands were divided into two zones, the cortex and the medulla. The adrenal cortex was seen to be divided into three zones: zona glomerulosa, zona fasciculata and zona reticularis. The Medulla contained the chromaffin cells. The gross, histological and histochemical studies of the thyroid, parathyroid and the adrenal glands of the African giant rat showed sexual dimorphisms and cellular morphology which could explain the biology of the rodent.