Histochemical and topographical studies on the somatotropic and lactotropic cells in ewe during reproductive cycle

A histomorphological examination has been made on the pars distalis of the pituitaries from twelve, normal healthy sexually mature balady ewes which were divided into three groups, according to the different phases of reproduction (resting, follicular and luteal phase). The histological features of STH- and LTH-cells during resting has been used to establish a standard with which the subsequent changes during the follicular and luteal periods were compared. Using PAS/OG, AB/OG and PFA/AB/PAS/OG stains, the STH- and LTH-cells were differentiated and identified from the other forms of the pars distalis cells. The topographical localization of the STH- and LTH-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 STH-cells showed no significant variations during the resting, follicular and luteal phases. --The LTH-cells appeared to be more abundant and showed signs of hyperactivity at the diestrus than the anestrus and estrus phases.