Morphological Studies of the Canine Pituitary Luteinizing Hormone (LH) Cells after Long-Term Treatment with the LH-Releasing Hormone (LHRH) Agonist [D-Trp6]LHRH Ethylamide

Since treatment with LHRH agonists (LHRH-A) cause changes in LH secretion which are similar in both man and dog, we have studied cytological changes occurring in canine LH cells after chronic administration of an LHRH-A, [D-Trp6] LHRH ethylamide. At the light microscopic level, LH cells were distributed evenly in the gland, but showed a decrease in cell surface area of 10% after 1 month and 23% after 4 months of daily injection of 50 micrograms LHRH-A. At the electron microscopic level, the gonadotrophs from control animals were characterized by the presence of two types of secretory granules and a dilatation of the rough endoplasmic reticulum. Immunostaining for LH was localized only to secretory granules. LHRH-A administration caused the appearance of glycogen in the cytoplasm. Four months after cessation of the treatment, the gonadotrophs showed a normal cytological appearance, thus indicating full reversibility of the morphological changes induced by long-term treatment with an LHRH-A.