Comparative Anatomical Studies of Adrenal Glands in Large White Yorkshire Pigs Reared at Low and High Altitudes in Kerala

The adrenal gland plays a crucial role in the body's homeostasis and during the stress response. However, less attention was given to the structural variation of the adrenal glands in pigs reared at different altitudes. Hence, the present study was conducted to correlate structural variation in the adrenal glands in 24 ten-month-old Large White Yorkshire pigs of either sex reared at low-altitude and high-altitude regions of Kerala, India. Microscopically, the adrenal gland presented the three typical concentric cortical zones: zona glomerulosa, zona fasciculata, zona reticularis, and a central medulla. The arrangement pattern of cells of the zona glomerulosa resembled the arcs; zona fasciculata, similar to cords separated by intervening trabeculae; and zone reticularis, like irregularly anastomosing cords. Two types of cells were present in the medulla: large, granular, intensely-stained cells towards the periphery and small polyhedral cells towards the centre of the medulla. Chromaffin was identified in the medulla, while undifferentiated cells were identified within the capsule, subcapsular zone, the transitional zone between zona glomerulosa and zona fasciculata, and even medulla. Zona fasciculata formed the largest zone of the adrenal cortex, and its thickness was significantly higher in the low-altitude male and female groups than in the corresponding high-altitude groups, which was correlated to serum cortisol levels. The comparative micrometrical data revealed a larger zona fasciculata in the low-altitude male and female groups than in the corresponding high-altitude groups, indicating variation between the groups.