Comparison of mammalian luteinizing hormone releasing hormone (LH-RH), and of an analog (ICI 118630), on luteinizing hormone and ovarian steroid (progesterone, oestradiol) secretions in laying hens. (Gallus domesticus).

This experiment was conducted to compare the luteinizing hormone (LH), progesterone (P4) and oestradiol (E2) release in response to injections of various doses of synthetic mammalian luteinizing hormone-releasing hormone (LH-RH) and of an LH-RH agonist, ICI 118630, administered to laying hens 4 to 9 hours after a mid-sequence ovulation. Plasma LH increased significantly within 10 minutes of injection of either compound whereas any increases in plasma steroid concentrations were discerned later, at approximately minutes post-injection. No dose-response relationship was found for either compound with respect to LH release, but ICI 118630 appeared more potent than LH-RH. This analog also produced a greater mean incremental rise in plasma progesterone, but not oestradiol, than LH-RH, and this was found in animals injected at a time when the largest ovarian follicle was not mature. These result suggest that ICI 118630 is a more potent releasing hormone in the hen at the level of the pituitary, and that it may have a stimulating effect on ovarian progesterone secretion.