Action in vitro du facteur hypothalamique de libération de l'hormone lutéinisante (LRF) sur l'antéhypophyse d'agnelle : II. Etude ultrastructurale des tissus incubés

Abstract

The ultrastructural evolution of ewe-lamb pituitary slices incubated as function of time (30 min, 60 min, 90 min, 2 hr, 3 hr, 4 hr, 8 hr and 24 hr) was studied in absence or presence of a purified hypothalamic luteinizing hormone releasing factor (LRF) and in one case in the presence of a brain cortex extract. High resolution autoradiography was utilized in order to appreciate the protein synthesis ability of the cells. Anterior pituitaries were obtained from ovariectomized ewe-lambs pretreated either with fluorogestone acetate (FGA) or with progesterone and estradiol benzoate. LH, FSH, and prolactin cells were identified at electron microscope level. All these cells were stimulated by castration. The treatment by progestogen was followed by storage of granulations in Lh cells and by an increased activity of prolactin cells. In the absence of brain cortex extract or of LRF, particularly beyond 4-hr incubation periods, all pituitary cell types underwent a progressive necrosis with the exception of prolactin cells, which maintained an intense secretory activity. Before the 4-hr period the release of granulations in LH cells followed a normal process. Brain cortical extract added during the first 90 min of incubation improved preservation of tissues. LRF did not prevent necrosis of most of the pituitary cells and did not inhibit the intense secretory activity of prolactin cells. LRF selectively stimulated the survival and secretory activity of LH cells. To an increasing rate, and already after 30 min, this stimulation affected all the intracellular organites implied in the whole secretory process: ergastoplasm, Golgi zone, granulations. Moreover. LRF exerted a morphogenetic action as shown by an increase of cytoplasm area and of intracellular membrane system.