The effect of a luteinizing hormone-releasing hormone antagonist on experimental endometriosis in the rat.

The effect of a Salk LRH analogue (Antagonist I) on growth of endometrial explants in the intact female rat was studied. Subcutaneous injection of the analogue was begun 3 weeks after transplantation of a section of endometrium to the peritoneal wall. The animals were laparotomized and the volume of the explant (length X width X height) in mm was measured with calipers on day 1 of treatment. The animals were injected daily for 3 weeks with 50, 250 or 500 micrograms of Antagonist I at which time the animals were again laparotomized and the volume of the explant measured. Eight weeks after cessation of treatment the animals were sacrificed and the volume of the explant measured. The degree of inhibition of explant growth was directly correlated with the amount of Antagonist I administered; a significant inhibition was obtained with doses of 250 or 500 micrograms. Eight weeks after cessation of treatment all explants demonstrated renewed growth, although explants in rats which had been treated with 250 or 500 micrograms had returned to only 51 and 61% of their initial volume, respectively. The results of this study demonstrate the LRH antagonists may be useful in the treatment of endometriosis although at doses considerably higher than those of the super agonists.