Ultrastructure of rat pituitary gonadotrophs after injection of synthetic luteinizing hormone releasing factor (LRF).

The effects of intracarotid injection of synthetic luteinizing hormone releasing factor (LRF) on the ultrastructure of pituitary gonadotrophs are reported. Chronically ovariectomized rats of the Sprague-Dawley strain pretreated with oestradiol and progesterone were sacrificed at zero time and at 30, 120 min after injection of 1 mug of synthetic LRF. A careful observation was made for evidence of granule extrusion from gonadotrophs following intracarotid injection of LRF, but no signs of granule extrusion were demonstrated. However, granule migration to the periphery of the cell was observed 30 min after LRF injection and the distribution of secretory granules recovered 2 hours after injection. The result of ultrastructural observations suggests that LRF plays an important role in releasing and synthesizing gonadotrophins in pituitary gonadotrophs. Further investigations should elucidate more clearly the morphologic aspect of mode of LRF action in pituitary gonadotrophs.