Compensatory mechanism of pituitary gland during various physiological status in sheep (ovis aries) – structural aspects

Histology under light and transmission electron microscopy was conducted on the pituitary glands collected from 35 Madras red ewes of different age groups. The chromophobes were round or irregularly oval shaped cells, which occurred in groups in the centre of the cell cords of the pars distalis adenohypophysis of prepubertal, pubertal and dry animals. Their population was more in the rostro-dorsal and rostro-ventral regions of the pars distalis with no affinity towards any of the acidic or basic dyes. These cells are thought to be non-functional reserve cells that become chromogenic when the cells become active. The folliculo-stellate cells were observed mostly around the follicles with a characteristic star-like morphology and long agranular cytoplasmic processes. These cells have supportive role by provided mechanical support to the endocrine population and also by producing many growth factors and cytokines In the current electron microscopic study showed some immature endocrine cells closely associated with chromophobes and folliculo-stellate cells forming an incomplete follicle suggesting that these two types of cells are likely to be involved in the differentiation of new endocrine cells as required by the physiological status of the sheep.