Cyclic morphological variations in the gonadotropic cells in the pituitary gland of ewe

A histomorphological examination has been made in the pars distalis of the pituitaries of twelve normal healthy sexually mature ewes which were classified into three groups (resting, follicular and luteal phase) according to the different phases of reproduction. The histological features of FSH- and LH-cells during anestrus has been used to establish a standard with which the subsequent changes during the follicular and luteal phases were compared. Using PAS/OG, AB/OG and PFA/AB/PAS/OG stains, the FSH- and LH-cells were differentiated and identified from the other forms of the pars distalis cells. The topographical localization of the FSH- and LH-cells, in various regions and levels in the pars distalis of balady ewe as well as their frequencies during the different phases of reproductive cycle were discussed. Statistical analysis of the different cell count during the different phases of estrus cycle in comparison with the resting phase (anestrus), can be summarized as follows: - The FSH- and LH-cells are more pronounced, more active and significantly increased in number during the follicular phase of estrus cycle. - The LH-cells appear to be more abundant and show sings of hyperactivity at the luteal phase than the resting and follicular phases.